The problem with 18650s is they sag hard when you try to pull their rated amps. Or even a fraction of their rated amps, as compared to pouch cells. You do not see 18650s rated for 10c continuous.
You can't really just say this, because it's like comparing apples and oranges. You may be confusing voltage drop with sag. 18650s drop the voltage more over the life of the charge, but the LiFePo4 actually sag more. Cells no matter the configuration, pouches, or 18650 come in different chemistry's, and discharge rates. The stock battery that came in my red bike was a high discharge LiFePo4 chemistry made with pouches. My new battery pack is made with high discharge 18650 30Q Samsung cells rated for 15 amps. It out performs the stock battery by a small margin. My limiter is set for 65 amp, but usually recorded 67 amp with the LiFe pack. The 30Qs see 69 amp before the limiter can hit, and I see a couple hundred more watts.
LiFePo4 sag more then the 30Qs, but they average a higher voltage over the life of the charge. The 30Qs don't sag as much, and so are stronger in the first half of the charge, but in the latter half the voltage drops a little below the LiFe. Between the two, I prefer the 30Q. Honestly I've never been that impressed with the pouches. They seem to wear out faster then the 18650s to me.
Stealth doesn't disclose the specs on their LiFe pack, but my new 30Q pack is 20s, 8p. It can sustain 8 x 15 amp continuous, or 120 amp. Way more than I need, but with a 65 amp limit the cells are never really working very hard.
The triangle in my Fatty is much lower spec in comparison. Even though it's also made with Samsung 18650 cells, they're much lower discharge. It's rated for 30 amp continuous, but I have a 35 amp controller. That battery pack is working hard, and gets pretty hot in the summer. Even so, It's doing very well handling it's miserable life heading into it's 4th summer.