I own some Force FX sabers and one GE saber.>Force FX
Obi-Wan Kenobi's (RotS) lightsaber with the removable blade
Kylo Ren's lightsaber (got it before TLJ came out)
2 Maul sabers>GE
Luke's emerald classic lightsaber
Overall, I like GE a little better despite minor flaws, but it's more expensive. (Granted, Luke is my favorite character so there's some bias there)
The blade is easier to remove, it flashes when you hit something, it comes in a really cool little box and it looks really good. I want to get Anakin's saber to test out the blade swapping.
Kylo's saber is pretty neat as well, despite being the saber of a terrible character in horrendous movies. Maul's dual saber is like 7 feet tall or something.
There aren't many differences between FX and GE, honestly. They're made from the same stuff and you can hit pretty hard with them.