Just saw a photo here on Serebii where the trainer is using a male Lapras, which annoyed me WAY more than it should. To me Lapras is 100% female, just like all of the Fairy-types, with the exception of Mr. Mime, Snubull and Granbull.
Secondly, I almost never use a Pokémon where the Poké Ball doesn't match its design. For example, about a year ago I played through Emerald once again, just to catch the three legendaries in Repeat Ball, Dive Ball and Nest Ball respectively (previously caught in Ultra Balls). Yeah, it was kind of messed up to catch Rayquaza in a Nest Ball (succeeded though), especially when I caught a Nidoran (male lvl 7) in a freakin' Master Ball just because the purple would match Nidoking.
Therefore the thing I miss the most in never gens is the Poké Balls from previous games: Heavy-, Lure-, Level-, Friend-, Fast-, Love- and Moon Balls.
I know it probably sounds silly, but I care more about the two above than EV-training and Natures.
So is gender and/or the Poké Ball important to you too?