EDIT: I’m torn between the 2DS and 3DSXL. IIRC 3DS games are made with the original 3DS screen in mind while the XL just stretches the images. Yuck. Plus I don’t care for 3D but DAT BIGGER SCREEN! I’ll probably get a 2DS, it’s a lot cheaper anyway.
3DS XL, it’s got more battery life and feels more comfortable in your hands than the 2DS and the 3DS will, plus the bigger screen helps as the screen is not large enough where images start to get pixelated (basically, the increase in size doesn’t change the quality of the image you’re viewing)
honestly, i’d go 3DS XL just for the longer battery life (it’s quite a bit longer, like 5+ hours or so)
Off the top of my head very few psychic types have the speed to fight regular Serperior except Alakazam and Mewtwo.
MegaSerperior: Grass/ Poison, four weaknesses as opposed to five, threatening against the new Fairy type, maybe increase Special Attack and Speed and Special Defense.
Ability? Contrary will make it broken so I’m not sure.,.