All things being equal (battery, prop, motor) a higher gear ratio will provide more thrust and draw lower current.
The effect on the flying characteristics depends on the plane. For example do not expect that more thrust will always make your plane fly faster or better. This depends on many other things. If you need more details, please provide details about what plane you are talking about and what do you want to improve by doing the gear change.
And note that we talk here about static thrust.

SM55