Never mind, I think I've found out the differences by comparing the feature lists and looking at reviews and stuff. I'll list them here for others to find.
Features that the Lightning has over the Gaming edition:
- Higher stock clock
- MSI Reactor, which has LEDs and capacitors in it, which supposedly improves power stability and reduces ripple, etc.
- Bigger heatsink, but still has 5 heat pipes like the Gaming
- Comes with an SLI bridge and a gimmicky "Military Class III" certificate
The Lightning doesn't offer much over the Gaming aside from aesthetics and possibly binning/reactor thingy to eke out that extra bit of overclock.
I'm going to wait for MSI's 4GB model, however, as I want to be able to fully mod out Skyrim and have the ability to upgrade to a 1440 monitor in the next couple of years.