The 510
atomizer is the most widely used (at least among ECF members, not so much by mall or convenience store purchasers). But the Fat Batts (e.g., eGO) may have surpassed the 510 battery.
Actually, I'm not sure how well a 901 cartridge works in a 510 atty; I've never tried it. The drip tips are identical. I don't know of any other type of cartridge that would fit in a 510 atomizer.
To my mind, the more significant issue is atomizer-
battery compatibility. The other atomizer that works (without adapter) on a 510 battery (including 510-based fat batts and 510 fittings on
mods) is the 306. Also the 510 cartomizer (regular or CE2). And on the eGO/Tornado and Riva, mega eGO cartomizers and mega eGO atomizers/cartridges also work.