The Vita is PowerVR SGX543MP4 in quad-core config will nets you about 30 GFLOPS.
The gap between the Wii U and Vita is comparable/bigger than the gap between Wii U and PS4/XB1.
So yeah, if Vita is "almost" a Wii U, the Wii U is "almost" a PS4.
The Vita is closer to original XBox (the one released in 2001) than it is to the Wii U.