I have both actually. I got the O2 trainer first. my only difficulty with it my throat would get a bit sore and the nose piece would move a little when sweating heavily. I tend to like the mask better because you can do more of the breathing through your nose. I know some folks get a little freaked by a mask on their face and it may take a little to get used to. I also like the mask because it's more difficult to cheat on the breathing since the O2 trainer fits as a snorkel would. Just my 2 cent as it were. I also made a home made version of the mask. I ordered a gas mask, {NBC} type, off ebay for 15$ and free shipping and just used duct tape and made a hole in the duct tape. It works as well as my elevation mask actually. Oh and it does work by the way. I even argued the point with some folks and I found some science to back it up, but I would have to go back and find the research paper..Walt