The pioneer is slightly more compact - the commando has the shoulder-bits that stick up - and it has a front-mounted control to open the crack-bottle.
Oh, and if you do get a Buddy jacket, I recommend the TD range - it has more useful D-rings than the standard version..
And I'll say it before anyone else does: If you're in a situation where you think a spare supply of air would be useful, get a pony rather than a crack bottle.
Ha! Beat you all!
A crack-bottle dSMB is a different matter, I have one and it's great
