In reply to BnB:
Out of those two, the Warthog. Lighter, simpler, no zip, can be over packed, jazzy helmet holder, looks more durable. No brainier (The Cobra is ~850g!).
However, I got an Ascentionist 25 for just this use for silly cheap off the EpicTV shop (thanks neuromancer!) but I've yet to use it properly in anger.