PS Vita or PS2.

PS2 mainly for the games, so many fantastic ones I still play and replay decades later. Keeping track per platform the owned-played ratio and how many liked games in absolute numbers each has for me, the PS2 is still king in both. Even lesser known games I generally have a blast with.

On the Vita, its library isn't as strong as the PS2's, even if many of my favorite games were found through the Vita. But it compensates at being a fantastic console to mod. While I know people modding consoles do it for playing ilegitimate copies of games, if you ignore that, its mods still give you a lot to use the console for, possibly risking seeing the console dying in your hands while you read an ebook on it, try some homebrew ROM from Itchio, play with PSP homebrews, etc. Also it's a bit of a learning curve and technical information on it is sparse, but learning how it ticks makes tinkering second nature (...unlike the PS3 =.=").