It will probably be easier to micromanage the enclosure with the smaller ten gallon for now, if you are getting a baby one. I find it easier to watch over temperatures, humidity, etc with a smaller snake if they are in a smaller tank.

Pyros seem get stressed at higher temps. More then half the time, by baby pyro would be near the middle or the cool side of them tanks. I just use an undertank heater at the warm end and it gets the surface around 82-84F. The cool side is room temp.

Good luck! Pyros are awesome!