One of my first adventures away from cig-sized PV's was a SD MKII (native 901
thread). But it came with a 901 to 510 adapter, and frankly I liked the 510 on it much better. Then too, there's more 510 stuff out there to play with. So I sort of left 901 behind. (Ego, Go-Go, etc.)
BUT, I eventually built a
puck, using a 901 (just because that's how the instructions read), not really expecting much, and figuring I could use the 510 to 901 adapter.
Well, knock me over with a feather. The 901 at 4.8 volts (probably more like 4.2) is light years beyond a 510 at 3.7v OR 4.2v. I now have to force myself to use my 510 stuff, but 90% of my
vaping is on the puck with the 901. Even the wife admits its MUCH better than any of the 510 stuff.
Maybe not for everyone, but for me at least, 901's RULE.
BTW, I've gone thru so many 510 attys I've lost count. But I'm still using ALL of my original 5 901's (from Totally Wicked) and an SLB 901 (even better)