Also, when you are considering gas bottles, check your local codes. In TN, 80cuft and down are considered "user owned" and do not require ID numbers to get them refilled. You basically "buy-in" the first bottle, then it is an exchange program like with propane at the box stores.
If you go larger than 80cuft (in TN, at least), you must register the bottles, pay monthly lease fees, and wait while on site that bottle is refilled.
Even though I go through quite a bit of gas in a year, it was cheaper for me to "buy-in" with three 80cuft bottles, and do the exchange thing, than to go with the 120cuft or bigger bottles.
Also, keeping a higher number of smaller bottles keeps the gas "fresher" and reduces leak off (no matter how good you "seal" em, the more connections you have in line, the more gas you're gonna waste).
The down side is that someone could steal your smaller bottles and there is no real traceability. With the larger bottles, here at least, you literally have to show your ID when getting the bottle filled. It does act as a theft deterrent.