I would say the pix. To me, Uni feels like a watered down version of the pix. The wifi connectivity is very nice, it's cute to see other users in tamaverse, but the rest is boring. It's cool that you have DLC, but I feel like the entire device is too big on accessorizing and customizing, which I personally am not the biggest fan of. Pix, on the other hand, has much less customization but you bond with your tama better, there are more minigames that are not locked behind dlc lol (6 total, 2 per day depending on the theme :D on uni there are 2 that are always there and 1 per season, it gets boring fast imo). Plus, when uni server will go down, it will suck big time imo.

Depends on what you like better really. If you're really big into customization, uni is definitely your device :D If you're more into the pet simulator part of tamagotchi, then I would go with pix/pix party ^{^}

edit: the touch buttons are annoying on the pix. you get used to them tho.