I have to admit I am looking towards getting some 120s. I find the al100s really get light at the end and my dive profile now involves alot of lead.... My understanding is the 120s are much nicer from that perspective. Rather than hanging weight to keep the tank down, the 120s do it themselves. Now that the wife is on nitrox all the time, I need at least 100s on nitrox to keep out of deco on my Mares and stay up with her....