It is true that XP2 scans with less grain, but it also (in my opinion) scans with less definition. I'll take some noise to get rid of that slightly muddy look. And sorry, I did mean the Coolscan V when I said IV (although the IV is a fine film scanner as well).
I have not personally tested the V700 (I have an adequate flatbed), but many others who know their stuff have (look at the www.largeformatphotography.info
forums and similar places for people trying to push flatbeds to their limits). I've heard nobody but Vincent at photo-i claim this performance for the Epson. I've also seen nobody able to reproduce it. Any scan I've heard about of resolution test targets shows the Epsons at about 2400 dpi (what Kirk said). These same tests show scanners like the Nikon at 3900-4000 dpi. And scans of negatives show these differences.
You also have to see the raw scans---off the flatbed, they are quite fuzzy, and must have significant sharpening to be usable even for small prints. The film scans need little (or even no) sharpening to provide a good print. This sharpening has effects beyond bringing back details, and I don't much like the look of it. I think the Nikon gives 4000 dpi of high quality pixels, while the flatbed gives 2400 dpi of visibly lower quality pixels.
I don't doubt Vincent's results or competence, but I don't think his goal was not comparison of these scanners. His test negative (distant construction cranes, if I recall correctly) meets no standard, and it is possible that it limits the ability of the test to discern the real differences between these scanners (maybe 2400 dpi is all the negative has to give).
I'm also not trying to beat up on the Epson scanners. I think they're pretty good, and might even be acceptable for your 6x6 scanning (many consider them quite good for up to 4x enlargement). Find somewhere to try it for yourself, and make prints---don't just look at screen images.
I'd wager that if you stick to 35mm film, you'll have a dedicated film scanner sooner or later.