So here’s my massive post on it lol. As someone who heavily collects both.
Card wise for collecting I’d say Yugioh because I feel like I get more for my money with those compared to what I get with Pokémon cards. Also I have a sea of those card codes from Pokémon card packs that I’m never going to use which I feel like is space that an extra tcg card could have taken. I noticed by comparison I get more diverse cards and less duplicates when I buy a Yugioh booster box vs a Pokémon one. I also ended up with a extremely large yugioh collection very fast compared to my Pokémon one.
However Yugioh cards aren’t the same quality they used to be. (By this I mean how they’re made.Design wise they’ve been awesome)
If you care about PSA graded cards Yugioh cards haven’t been the best looking here lately. With things being slightly off center, scratches already on the cards and such. While for playing and casual collectors it’s no big deal but for grading it is. So it’s been hard to get cards that would be graded high. I would even reach out to a community beforehand and post pictures of the card to see if it’s even worth paying the money for it to be graded. Also they don’t fit very well in the PSA slabs so you could end up in the unfortunate situation I’m in with a damaged PSA 10 card. The corners are all messed up on the card from when it was put in the case. PSA may or may not help you. They blew me off when I reached out about my card arriving back damaged. So it’s pretty much a worthless card now that it’s damaged.
With graded cards I’d lean more towards Pokémon just because most horror stories like mine seem to come from yugioh and sport cards being sent to PSA. I’ve not seen as many complaints with Pokémon ones. There are other card grading companies but they aren’t as strict with grading as PSA is so people tend to not buy them as much(if you one day decided to sell your graded card.)
I also highly recommend putting the Yugioh cards in a single sleeve and then put them into the binder sleeve. They slide around in most binder sleeves made these days since their so small. I’ve had some fall out just from turning the page.I never had that happen with my Pokémon cards.
If you’re looking to play tcg I would say Pokémon. It’s far easier to learn and play compared to modern day Yugioh. Modern day yugioh is too much. Not only that everyone seems to be running the same decks in Yugioh.(Eldlich) So it gets boring fast. Not only that it takes people like 20 minutes to do their turn(I’m not even joking. In modern day yugioh it takes people ages to take their turn.) With Pokémon I’ve come across a wide variety of different decks people use. It makes playing so much more fun,it’s not as complicated and I’ve not waited a decade to take my turn.