Bigger is better.

A larger plane will also tend to hold your interest longer.

If you can, even consider a gasoline engine 70-80" plane. e.g. something in a 26-36cc sized gasser.

The up front cost for the engine will be recovered in short order by the savings on fuel, while those planes are small enough to use standard higher torque servos.

You'll also love not having to run to an LHS or on-line supplier for fuel... the engine has a built in pump, so once broken in and set, you forget about it... and deadsticks, etc.

Good gas engines can now be had for about the cost of a two or four stroke engine.