Im coming in a little late here but heres my .02
Beacon. Simple as that, I own both and ride with both AT ALL TIMES. I have friends that dont own beacons. I own an extra beacon that I will bring with me. I also have buddies who think, "oh we arent going in avalanche train we dont need to turn ON our beacons:, yes they have them but dont want to turn them on. That is, im sorry but absolutely retarded. Theres is 0 harm in turning it on.
Yes if you were riding by your self at all times I would say a bag, but come on who here ever rides by themselves? I have NEVER gone for a complete solo ride, I have gone for rides without other sledders but I still dont like that, no matter what though there is somebody else with me with the proper equipment.
Im not even sure where this post is going, but when I saw the title my jaw honestly dropped, I couldnt believe this was even being asked. Seriously guys, if you cant afford a beacon dont ride for one weekend, youll save the money in gas in that one weekend to be able to buy a beacon. Seriously people never seize to amaze me. Im a broke student, I just broke my sled and I wont be fixing it till I get paid next, at the very soonest, IM BROKE, but guess what, I still have all the proper equipment and know how to use it. Safety is always first, and if "Safety" might not be first in your mind at least think about the people who you are hurting if you die in an avalanche. Its not always about just you.