I've had both and prefer the full-sized body a bit more, but am getting less discerning. Roger calls the RV body a 7/8ths size (compare to Fenders), I think. I definitely notice a difference in how the upper bout hits my chest , but unless you've been long accustomed to Fenders, you'll never notice the difference (especially if you play mostly standing up.)
The UV70 pick-up placement in the bridge makes the tone a bit more aggressive...which I like. I'd start with an RV4 if possible to see if you notice the mass difference...unless a deal comes up for a UV70. The RV4 should be a tad lighter.
Good Luck. Can't go wrong either way.