i have tried the atlas, the leatt, the astars
i wear a leatt, not particularly because its the "brand" but because that's what i got for christmas a couple years back. my buddy just recently got the atlas, and i can say that it is drastically different and has a different feel than the leatt, the astars is kind of in the middle as far as feeling goes, between the leatt and the atlas.
the astars and atlas feel lighter and feel lower profile than the leatt.
i've been happy with my leatt, its weird when i first got it i thought it was a mistake because it felt awkward, but now i wont ride without it. It's "cheap" insurance as far as i'm concerned. They're not for everybody, they may not protect from certain things, but i'd rather have it than not.
If somebody was looking to buy one, i'd ask to borrow one from somebody and testing it out a couple times (not just a lap or so, but for a couple weekends worth of riding) to really get the feel of it. Like i said they're not for everybody but i would urge people just to try it