There isn't a huge difference in the lighting effects. Really, they're not big at all.
And the graphics in Rebel Strike are better (although I still think the water is atrocious), but the framerate is much more unstable. The ground missions are awful and the space ones are more unstable than the ones in Rogue Leader. There are noticable improvements, of course. However, does that mean that one should sacrifice framerate for them? I would much rather have a few less lighting effects and polygons (the higher poly counts aren't even that noticable thanks to the TV's resolution) and a stable framerate rather than some relatively small improvements and an unstable framerate.
And graphics, of course, don't save Rebel Strike from being inferior to Rogue Leader in just about every way when it comes to gameplay.