I have a
dual body regulator on the tank outside my brew fridge. I have four kegs inside the fridge, being fed CO2 via two manifolds. This allows me to feed up to three from one body and up to two from the other (making it possible to carbonate pretty much any style I'll brew). I use one pressure set for all my ales, with another for any porters (or stouts) I have on tap. I can also use the second body to hit a keg with higher pressure if needed, such as to carbonate faster (IF I really need/want to).
I really like having the CO2 tank outside the brew fridge. For one thing, it's easier to see the gauges and adjust as needed. For another, it's easy to change CO2 tanks as needed. Plus, I don't lose all that space inside the brew fridge. Not to mention I'd be more limited with what size CO2 tank I could use in the brew fridge. With it outside, I have no issue using the 20# tank. I could even go to a much larger CO2 tank if I ever wanted to.