As someone who has little investment in either console, the Xbox.
The Xbox was an important stepping stone in the evolution of game consoles. It featured PC-like hardware that allowed for easier ports of PC games, an emphasis on online capabilities, a built-in hard drive, patching software digitally, etc. The PlayStation 4 and 5 have more in common with the Xbox than the PS2.
Just as importantly, the Xbox was able to take advantage of this with its library. It had PC-like hardware, so you got console exclusive ports of PC games like Morrowing and Knights of the Old Republic. You had online play, and games that took good advantage of it like Halo 2 and Counterstrike. You even had the ability to run pretty much anything on the PS2, and thus the Xbox got plenty of multiplatform games despite its fairly low sales.
As for the Vita... it had a second analog stick, so you could play a stripped down version of Uncharted on the go? And sometimes the best version of games ported from the PS2?