Originally Posted by aggiegrads

I carry both - a mini pump on the frame and a CO2 with one cartridge as a backup. I have never used the CO2, as I have only had a hand pump fail once, and it was on a charity ride and there were pumps everywhere. You are much more likely to double-flat than have a hand pump fail. If you double flat (either flat both tires or have to have the same tire flat twice) and have CO2, you are out of luck.

edit: I just weighed my setup and my Blackburn airstick - 59 grams. This is one gram heavier than a CO2 cartridge - 58g. For the same weight of a second cartridge, I have a pump and a CO2. In my case, however, I have a backup for ~85g - CO2 cartridge and head.

I know that money is tight, but if you can only afford one and have no physical limitations, I would really go with the more reliable solution (pump) than a CO2 inflator. Of course, your OP never actually said that you did not have a pump, so this is all inference on our part.