Keeping the CO2 Canister outside may have a small benefit by having it warmer.
My kegs and fridge are in an outdoor room at the house and it gets pretty warm. I notice that as the temps rise, so does the pressure in the tank which is kept outside the fridge.
It would seem logical that having a lower temp for storage would by default lower the potential pressure available.
The N20 I run in my car benefits greatly by having the bottle warm for instance.
Just my 2 cents.