I own a RV-6 and I felt like it was the best trade-off of all the RVs from the used market perspective.
The RV-4 has better visibility. But the tandem seating the CG becomes a issue more often and there is less/just about no cargo space.
The RV-7 has slightly more fuel/cargo capability but there are less of them on the market versus the RV-6. There are some other small changes between the two but the lower cost of the 6 outweighed them.
I'd love to build a RV-8 when I have the time some day when i'm older but they are damn expensive used.
RV-9s are for X-C cruising, no aerobatics.
RV-10s are for small families.
RV-12s are for old dudes that lost their medical.
RV-14s are for fat old dudes or if you just want some extra breathing room.
I have a blast every time I go flying. It is really cool to be able to cruise somewhere at 165 KTAS burning 8 GPH or just around buzzing cows.