For anyone interested, I was in the middle of testing battery packs as this topic came up once again. I only have 5000 and 4000 mAh packs to play with. I used a Checkpoint 1030 and Duratrax Ice chargers set to a 10 amp discharge and recorded the average voltage at 600 seconds. I figure a 10 amp discharge at 10 minutes will be a close simulation of what we do in VTA minus the peak draws of hard acceleration.
My best 4000 mAh pack = 7.722V
My worst 5000 mAh pack = 7.813V
My best 5000 mAh pack = 7.901V
That difference of 1 or 2 tenths of a volt doesn't seem like much but I like to think of it the same as tenths of a second. Factor in that this is also a multiplier of the C rating and there is a real advantage to the higher mAh pack even if it is a small one. The difference between a 3800 and a 6500 is going to be much bigger. Maybe .5V. That would make the 3800 totally obsolete. At least with the 5000 mAh cap, the guy running a 3800 could still feel competitive as long as he realizes he has to be better than the "next guy" at suspension setup and driving in order to win.