I’ll offer my humble opinion, as I’ve ran all three mentioned here, and I currently own a 6100 and several 6400. A good 262 and a good 6100 are close enough to where it won’t really matter to me. 6100 has shown to get very good gains when ported right. Maybe the best of any 60cc saw out there. The 262 ain’t no slouch either.
The 6400 has quite more torque than the other two stock, and will oil a longer bar right off the bat.
If you already have a smaller saw, 40-50cc, I’d look at the 6400. Mostly because it can handle a longer bar, if ever needed, and the ability to upgrade to 79cc down the road. Trust me, you’re gonna want that upgrade. Lol
I’d take a 262 for simplicity and light weight, and a 6100 if you want a more modern saw and the potential to make a hot rod later.
As a side note, the 262 and 6100 both use K095 mount bars,
and the 6400 uses D009. I figured I’d mention it, in case you’re looking to share bars with other saws.
As far as feel goes, the 262 is going to be more nimble. No doubt, since it’s smaller and lighter than a 6400. The 6400 will be smoother, though, in my opinion. The 6400 also feels like it’s built to take a beating.