I have a buddy that does a lot of elevation training. He has used the one pictured above (
seen here) and said it works, but it is much like the difference between Vancouver and Rossland (sea level to 1km above sea level). It is decent for beginners. He uses
this and said it works great. He has done several high altitude climbs (the names escape me but I think K2 is in his pipeline soon, and Everest is his, well, Everest) and he uses it in the days leading up to the climb. Said it is fantastic.
I asked him about the first mask and he said that it is lighter than the second one, but sits on the face weird and leaves him woozy, but not short of breath. It digs into his neck and slows his blood flow.