I've started looking at avy pack as well by request of my girlfriend. I've narrowed my choice down to the ABS Vario, Mystery Ranch Blackjack, BCA Float 32, and North Face Patrol 24 ABS.
IIRC, there are three or four main manufacturers: ABS, Snowpulse, Avyvest, and I think BCA. The Mammut packs you're looking at use the Snowpulse system. North Face uses ABS, and Mystery Ranch uses Avyvest. BCA I believe makes their own, but I'm not 100% sure.
I haven't read much about the Mammut packs, other than they use Snowpulse technology. Being able to switch bag sizes is pretty a pretty nice option, although I believe the Mammut bags just have a removable airbag section that you can stick in other bags, so you technically are still buying another backpack.
The ABS Vario packs have a much better system IMO, where airbag is in the base unit, and you can zip on separate bag sizes. There's a reason you see most pros with ABS packs, they're very well made and I believe have been around the longest perfecting their technology. The only problem I find with the ABS packs is their price and availability in North America. The base unit and canister will run you close to $1100, then closer to $1300 once you get a bag on it. I have yet to find a vendor that sells a large variety of the zip on packs, which in my mind defeats the purpose of being able to switch bag sizes. I'm hoping more vendors will have product available this year. REI and Backcountry have been known to have some, but not a huge selection.
BCA definitely has the best priced packs in the states. Pretty much under $750 out the door for the Float 32. I HATE their packs though. I just don't find them comfortable at all. I'm hoping that's changed with the brand new Float 32 though since I have a buddy with a BCA proform which would get me in under $600.
Mystery Ranch definitely intrigues me. Their pack looks awesome, but the overall weight of the pack is keeping me from buying it already. It's got a really sweet frame and is super customizable (which probably doesn't help the weight). It's a 43L pack, so it's big enough for longer tours, but compresses down very nicely. I really really like this pack, but the weight still bugs me.
An airbag isn't a replacement for extensive avy training and knowing what you're doing. Nor should it give you more confidence when riding in sketchy terrain. Same goes for the Avalung (which I ride with too). But it does give you one more out if the shit does hit the fan.
Anyway, check out wildsnow.com, they've done a ton of reviews on airbag packs.