Pokemon Gen 4

It is more challenging to an extent, like higher level opponents and more type coverage in enemy movepools, but you can still go with the same type of team as you had as before because it's still pokemon and level trumps most, if not all. The ability isn't especially important, but pretty useful for some pokemon like Gyarados because it lets it survive more hits. Physical/special split is big but still not that big of a deal. It just makes your pokemon better for the most part, if you take note of which att your pokemon is better at. You can look this up but even if you just use what you like, you'll be fine. Contests is also pretty unnecessary (I personally skip them). It's like a minigame for the most part.

^ He said he's not interested in competitive and it's hard to take note of EVs when you're going through the story anyway.