its not even a matter of opinion. magnetic cubes are so revolutionary that the only event where you can even get by with a nonmagenetic cube is MAYBE OH.
try them both at a comp because peoples opinions may not be what you like. you also should try other brands of cubes because you may like those better than gan which most people do.
PetrusQuber you can use petrus if you can find good fingertricks for 2x2x3. I currently use CFOP and average around 17 seconds OH. Im planning on switching to ZZ, or atleast getting comfortable to the point where ill switch if i want to. If you want the best method however, use roux.