If you are not using it weekly then yeh you are right the bottle rental and refills would be a waste of coin, but then again depends on what you are welding.. making up brackets, making fences/benches and general welding a gasless job would be fine, if you have them set up properly all you have to do is give them a hit with a wire brush when done and they look great!.. the seat rails i made today were done with my gasless, as was the exhaust i patched yesterday on a mates Liberty wagon..

If you are doing any bodywork i would use the gas, the weld is alot cleaner, neat and easy to control.. i have my gasless mig and my tig here at home and my Gas mig at work because i couldnt be stuffed carting the bottle around, and my work pays for it