I'm still not sure if I have it figured out. Which atomizer is the 901 or the 4075. I've ordered 901's from different vendor, sometimes they come with the rounded wicking bridge and sometimes with the pointed bridge. Well, I like the one with the rounded bridge, which I beleive to be the rn4075. Heaven's Gifts carry both types (901-pointed bridge)/(4075 rounded bridge). I only use mod's with 4.5v/6v and the 4075's don't seem to run as hot as the 901's. IMO the rn4075 produces a thicker vapor, smoother throat hit (no burning, acrid taste), and has a faster break in period. As for durability, both types seem to last about the same. Not long. I probably belong in the super heavy vaping group, usually using low nicotine though. For me, it's more about the vapor cloud and thoat hit. Hopefully all the pg or vg won't kill me. Anyway, 2 thumbs up for rn4075's a 1 1/2 thumbs up for the dse901..One other thing, you can get both types of atomizers at Heaven's Gifts for $6 each. They always seem to be in stock, and the e-juice is not bad either at $9 for 30ml. I don't know what there warranty is, never used it. I only return things that are DOA, and I haven't had a problem with their products.