JD, I try hard so thank you for the kind words.
OK, my picks for top versatile capsules in the RED line up are:
R8: All purpose, tuned in a manner that does not necessarily make one section of the frequency range more dominant. Neutral but with a good depth to it, natural and full sound.
R6: Scooped mids and a brighter / richer sounding top by comparison to the more neutral R8. When we first started tracking stuff with this capsule it compared very well to an original C12 capsule (C12A) although the original C12 had a more extended bottom end. Otherwise, RED nailed the flavor of this mic (we are also talking comparing to a 25+ year old C12A mic that might not represent the entire C12 race...).
R7: Forward mids and a more attenuated top end sound by comparison to the more neutral R8. We didn't have a real U-47 to compare to, but at one point we threw it up against the Lawson L-47 on voice, drums, guitars etc. No contest, the Red R7 had a clearer sound and the Lawson was a bit muddy by comparison. You could tell they were both going for that 47 sound though, but the guy who owned the Lawson said he would typically rather have the Red on most sources and I agreed.
So those 3 capsules in my opinion are the first buys in building the Red collection as they all do different things and complement each other the most.
A bit more info: The R0 is like a more extreme version of the R6 with a brighter top and bigger bottom. It's funny in a way to hear the R2 which is a condensor...tuned like a ribbon. Really did a good job on that one, it certainly is a ribbon-like sound! The R4 is a very clean and open and detailed sound that I've also had some limited experience with.
Hope this helps - War