I prefer regional variants all the way, they are permanent difference to a Pokémon that I feel add depth to the world. Some of the mega designs are nice but ultimately its just a burst mechanic in the games that doesn't add much to them.
I'd be quite happy to see Gigantamax forms retconned to Megas, even if it does raise the issues of Charizard having a stupid amount of mega forms.
I prefer actual changes to pokemon as a species instead of battle gimmick #274. Pokemon variations based on region have been one of my favorite concepts since back in the early Orange Island season of the anime where we saw those Orange Island Butterfree and other pokemon. Now if only more pokemon could have expanded visual deviations beyond shinies and straight up evolutionary deviations like regional forms.
I was pretty much 100% sold on the concept of regional variants the moment I found out I'd get to have an fairy ice type ninetales. Because... well obvious reasons. *glances at username and avatar*
I want to see regional variants of the Nido lines so badly you don't even know.
Personally, I love both, but if we were to only ever get one to show up in the games again, I'd go for regional forms because of how they interact with existing pokemon and the lore.
I'd still miss megas, though, just as I'll miss dyna/gigantamax forms if they get left in the past. But who am I kidding, I'd still buy the new gen anyway.
Fresh takes on old Pokémon that reimagine them in colorful, clever new ways while adding to the worldbuilding of the region completely mops the floor with "what if x but with stripes, spikes, and a goatee lol" (that's a little uncharitable of me; Mega Evolutions aren't quite that simple all around, but it is kind of a recurring thing, and in any case, I do feel like the ideas throughout the Mega Evolution spectrum aren't as diverse or interesting as those in regional variants). Besides, I think Z-Moves and Dynamax have both shown that there are other valid ways to execute a Mega Evolution-like mechanic, whereas it's hard for me to think of some alternative that could satisfyingly fill the niche of regional variants. Maybe some kind of artificial augmentation (though that would not have the same naturalistic appeal of RVs), or hybridization of species? Or Ultra Beasts; I might be willing to take a break from regional variants if it meant introducing another handful of Ultra Beasts (though ideally not all with the same Legendary-esque power tier). In fact, what if we have UB versions of existing Pokémon? It'd be like the inverse of the existing regional variants - instead of showing us how certain Pokémon developed in the new region, we could see how wildly they might develop in entirely different universes.
I'll go with Megas. I love the fact they have made numerous Pokemon, from Altaria to Kangaskhan to Pidgeot to Pinsir to Ampharos actually good in battle. The regional variants are very hit-or-miss to me, although I really dislike a good number of Megas, too (especially Salamence, Aggron, Swampert, Heracross and Manectric).
Megas are sadly just a battle gimmick, even though they gave us new designs. Most of them are not that great, IMO. Regional variants win by a landslide. It's neat to see new takes on old Pokemon. I also really love what they did with Rapidash and Marowak. These are not Pokemon I would have normally used with their original types (Rapidash, maybe, but there were always other Fire types I preferred, like Houndoom, whereas Galarian Rapidash is my favorite Psychic/Fairy type by a wide margin).
Regional Variants all the way. Megas are cool, but you just can't beat regional variants. I love everything about them, but the lore to them is my favorite. Just the concept of Pokemon having o adapt differently is wonderful to see, and they can even expand on the concept, as they have shown with regional evolutions. There's just so much they could do with them. I really hope regional variants are here to stay in the series.
it's interesting, really. if i was asked this question around the time of SM's release i would've said megas with no hesitation. if only because i haven't really gotten accustomed to the idea of regional variants, but... the very idea of pokemon changing "form" (so to speak) based on their habitat feels a bit more "natural" in a more biological sense than having them powered up on command with a stone. :x
Besides not liking Megas (and as said recently, regional variants don't have the best implementation), I think that from a lore standpoint, Megas shouldn't return because of how it's explained the appearence of Mega-stones and how. ASOR was a stretch but can be understood for being released and taking up that mechanic from the new generation, but bringing that back is too much in my opinion.
Mega Evolution all the way since it can actually help a lot of the weaker pokemon unlike regional variants. Without Mega Evolution pokemon like Beedrill, Kangaskhan, Pinsir, Altaria, Aerodactyl, Ampharos, Gardevoir, Mawile, Medicham, Manectric, Absol, Loppuny, Gallade and Diancie wouldn't have gotten the attention they got.
People like to say Megas are just the same pokemon but with just a couple of different things, but regional variants are pretty much the same. A lot of them just change color or get a new thing. In fact, a lot of regional variants get less changes than a lot of Mega Evolutions.
I love both features actually, and I never compared one with another. Come to think of it, however, as a concept, regional variants are more interesting than mega evolutions, since mega evolutions are all about making pokémon designs more complicated and calling it a day. Regional variants usually have a story behind it, and it adds more to a pokémon as a character than mega evolutions always have. The part to my disliking is the idea of not changing an entire evolution line (Exeggcute, Cubone, Mime Jr.). Giving new evolutions to already existing ones (Obstagon, Sirfetch'd) definitely helps the designers be more creative.
That being said, the best thing would be if we had both at the same time.
I pick region variants but with one caveat that I guess contradicts an earlier poster, I don't want to see region variants with a region exclusive evolutionary stage from now on. And if the variant gets a new evolutionary stage that the original doesn't have, I want the original Pokemon to get one as well at the same time.
It feels like Farfetch'd, Mr. Mime, Linoone and Corsola just get left behind the moment the Switch generation of games end unless Galar forms are always going to be a thing that carries over into the future. Which, looking at Gamefreak's track record, isn't anywhere near a certainty
Plus, I just liked the simplicity of the Alola region variants being Pokemon you were familiar with getting a cool new look and type set and that's it. But now, variants are just like megas and primal reversion and gigantamaxing in that they just complicate things with even more new gimmicky evolutions stacked onto other mechanics.
Regional variants, totally. They not only add more lore to the Poke-world, but they're an example of real-world evolution, which is something that is often glazed over in Pokemon or extremely selective (Shellos line being the first example of it). While Megas were a nice way to breathe new life into old Mons, they became too powerful and were, as always, a battle gimmick, which gets old fast. Regional variants, however, spice up old Mons permanently, enhance their lore, display real-world evolution in a fantasy world, often come with new types and sweet looks, and are just overall a much better idea. I mean, as much as I hated that Alolan Forms were only Kanto Mons, Alolan Marowak became a favorite of mine because of its lore, type, and a few call-backs to earlier games.
While Megas did make certain Mons more viable, it's only a once-per-battle gimmick, while regional variants give older Mons the same treatment but on a more permanent form. And thanks to Galar, giving regional variants an extra evolution was a very sweet addition, like Obstigoon and Sirfetch'd, as it added even more lore and opened up many possibilities for later installments. Besides, due to the lore of Mega Evos, it's not as easy to execute it and it gets retconned every single time it's brought up (XY said one thing while ORAS contradicted it totally), while regional variants are more logical and can be more easily adapted into the Poke-world's lore and nature, making it the smarter choice in the long-run.
So, my final vote goes to regional forms, as it's more logical, easier to execute, upgrades man Mons permanently instead of a once-per-battle gimmick, and it adds new lore, depth, and possibilities to the Poke-world.
Regional variants all the way. I like the fresh looks some of the older Pokemon are getting, and it's not just an idea that's one and done. Regional variants can be done with any region; the Megas/Dynamax/Z moves have only been one and done gimmicks. Don't get me wrong, they're neat and add more lore to everything, but it being one and done doesn't make it terribly exciting because we most likely won't see it again in a future game. At least with regional variants, it's something to get excited over because you can wonder what they'll do next.