The only real difference will be how many trips you'll make to the refill/exchange station. It's also a slightly cheaper initial purchase, but I bet if you worked out the math, you'd spend a little more for 5 lb tank refills over the long run. My 10 lb tank lasted ~ 2 years between refills. This is with it running 10-12 hrs/day, on timer with lights. Refill on a 10 lb at the place I've been going to is about $30, but I know it can be had for cheaper. I'm going to go somewhere else next time. Point is, its only a few bucks more than the 5 lb ($16-$18), but you only do it half as often.