LX-60 has:
*9mm linear excursion vs 7mm of the G40, hence greater SPL capability
*LX-60 works in SBB4 alignment because of lower Fs and lower Qts, it's better damped with no sharp knees in the group delay (better transient response)

G40 has:
*0.5db less power compression at 700W
*Dual Spiders and what Beyma calls an improved motor structure

Both drivers will work though, but I'd prefer the LX-60. In a pro sound application the more rugged G40 with dual spiders will withstand high volume levels for longer, but for a home application the LX-60 has more benefits. I'd expect it's probably a little cheaper too, if the G40 is a new model.

Overhang and top plate thickness of both models are actually the same though according to Beyma, so the quoted 9mm xmax of the LX-60 to the G40's quoted 7mm xmax should possibly not be used as a comparison; they should have the same linear excursion. The better transient response capability is what really makes me choose the LX-60. To me, having tight transient response is very important.