I have and do use both.
Pros for co2- it's SUPER fast, can air up several tires without "overheating", can easily run air tools without waiting for a compressor, can seat a bead without any problems.
Cons and reasons I never use my co2 tank- I usually have to wait for others to air up anyway, so I don't mind using my slower on board air viair system.
It takes too much valuable space in my small Tj
It runs out after a while
Some cheaper valves/regulators can freeze up after a couple tires.
Costs 13.00 to get filled. Not too bad I guess
You never know when you will need it, and Might not always have it in the rig, but my onboard air is just a flipped switch away
My ride- 2001 power wheel, 11" plastic tires, upgraded battery, boat sides, custom bumpers, tow hooks, new paint.