It occurs to me that since I have both the Omicron and Atmos units folks might be interested in my 'side by side' observations? Not meaning to stir anything up.....
I was attracted to the Atmos after having the Omicron for a month or so. Key attractions were smaller size and painted body (hoping to improve on the stealth of the Omicron). Price was not a factor (and the prices have both shifted since then anyway....). The Atmos is shorter (smaller battery) due to it's lower capacity by about half an inch, useful but more would be better. Less use before charging, but perhaps a reasonable trade off in some cases for a more discrete unit. Likewise, brushed stainless looks good and keeps well but sure looks out of place in most places. The heat shield cones are shorter, exposing more hot cartridge than Omicron. The Atmos times out a second or so later, but just goes out rather than flashing so it's hard to judge when it's OK to press again for an increased hit. The chargers are nearly identical.
However, the Atmos has several shortcomings for the intended use with the Omicron oil carts. It's probably 'just right' for it's original use, or at least more appropriate. First off, if you're trying to be low key, the whole bottom of the unit lights up blue when it's on. Like a huge blue cherry on a stoggie.....kinda like sending a flare up in a dark theater for instance. You can cover it with your palm, but forget or get sloppy and you could get into the very sort of conversation you're trying to avoid. Looks cool to some, no doubt, but a feature I can live without. Also the end cap is slightly rounded, you can't stand it up on end when not being used like the Omicron. Fine if you're using e-juice in a cotton cart I guess, but some of the hash oil I use will slowly flow if left too long on it's side. I keep the Atmos units standing in a cup for that reason. The push button is also 'proud' from the body far enough so it turns on against a flat surface (like the table), it will time out of course so it's not like having your MFLB go off in your pocket, but I prefer the better protected button on the Omicron. I can drop the latter into a cigar case for protection and be sure it won't hit the wall and light up. This is a handy smell tight way to protect it will moving about, BTW.
So, cost aside I see little advantage to the Atmos and several disadvantages. You get to decide how important they are to your needs, of course. For myself, I have no problems recommending the Omicron first....in case anyone has actually read this far.
OF