If you want your footage to be compatible with 30, 25 and 24 fps at the same time you could shoot at 48p or higher to get better frame rate downconversion results.
If your camera provides the right shutter speeds you can stick to 30 fps wherever you are in the world — most of the world is 50Hz.
On the other hand, if what you film will be edited in 25fps, that's when you should really switch.
It's counterintuitive, but it's been explained since the introduction of the 10-bit x264 open source codec (which is the most efficient software codec in the industry). Compressing an 8-bit source using a 10-bit x264 or x265 codec will be more efficient, thus giving better quality or smaller files than using the 8 bit codec.