If you're planning to run it on the gun, a 20oz tank will be heavy. Personally I run a 20oz with a remote so that I don't have to worry about the weight and I still have a tank that's large enough to get me through the day. A remote will also act kinda like an expansion chamber, in that it will let some of the gas expand before it gets to the marker. Additionally, if you're using a belt pack to carry the bottle, then the chances are it'll be vertical, so the gas comes from the top of the bottle, not from the liquid at the bottom. All this means less chance of getting liquid CO2 in your gun (unless you're shooting like there's no tomorrow), and less chance of frozen internals.

There are many more topics on the forum explaining the pros and cons of running different tanks in different locations. Just do lots of reading and decide what best suits your style.

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