Yeah, if you want a nice meaty racing game, go with PSP RR and PSone R4. I enjoyed getting all the trophies for RR Vita but at the same time it was depressing because the game could have been so much more. The best single player content in that game occurs when you unlock the "Devil's Gift". And even then, since the game lacks any single player progression/structure, it will feel like a HUGE difficulty spike unless you've played the older titles.
It's sad, I was really looking forward to RR on the Vita and they released... that.