I use the big one.......... the monster that is so heavy it's all I can do to lift it...It weighs just under 200 pounds full. It serves me to force carbonate as well as serving as a welding tank. It's the cheapest way to go, but you don't drag that monster into the kitchen ;-) In addition, I use 24 ounce paint ball tanks that lay right in the fridge with my toy kegging system (Tap-a-Draft). I bought an adaptor to fit the paint ball tank, and drilled and tapped it to 1/4 female NPT so I could screw right into the regulator without all the length you get with an adaptor. I use a welding regulator I had on hand. You can get a mini regulator that screws right onto paintball tanks from Williams Brewing for around $60.
Paintball tanks cost me $25 for a 24 ounce bottle with the first fill, and $4.00 per fill. They fill at the sporting goods store while you wait.... just a few minutes. I have 4 of them because I live a long way from town.
The big bottle is incredibly cheap to fill considering the volume of CO2....$45. I can also get a siphon tank at the same price and use it to fill smaller bottles. Bottle rent is $9 a month. $380 for a lifetime lease on the big bottle or $9 a month lease... a bit under 4 years to break even.
H.W.
