I currently have a strap on avalung(non pack attachment). After using this version of the avalung, would definitely say that if you want an avalung, using one that is integrated into the pack is the only way to go. The non integrated version of the avalung is a pain in the ass.
That being said, I really feel like whether you choose to buy an avalung or airbag is a personal choice. There are so many factors (personal decision making, terrain choice, weight, bc experience.. etc) that would cause a person to choose one over the other. If you want to save weight, go with the avalung. If you ski in terrain where the run out of a slidepath is densely covered in trees, go with the avalung. If you like the ski in the alpine or in areas that have clean run outs for slidepaths, go with a float. If you feel like having a float pack would cause you to decide to ski more dangerous terrain, I would probably steer away from a floatpack.
I own an avalung. I probably will get a floatpack in the near future. I would say that for most scenarios, a floatpack is better. The BD jetforce is a really good($$$) option. If you go the BCA route, I would recommend not getting the 32L. Everyone I know with a BCA float 32, says its way too big and clunky. If you are looking for something in the 30L range, Mammut makes a really good one in that size.