you are gonna have to choose between a good bag for on the mountain (ski carry, shovel/probe access, etc) and a transportation bag (boot/helmet compartments). i would recommend going with the one for on the mountain, something like the heli pro is good.
i've just always looped my powerstraps through the top strap and clipped my helmet on somewhere and that has been fine for many travel days (flights, long bus rides, long walks around airports/cities). if you are just looking for something to use to get your gear to the mountain and short trips, that will work fine. if you are constantly doing really long trips and living out of your bag for a while and feel the need for a backpack that carry's everything. consider getting something like a boot bag and a seperate backpack for on the mounain