First off, I got FRWTL for myself with the hopes that my wife would join in. It just seemed to give more bang for the buck than the RKC DVD. I got it because it was twice as long and cost $5.00 less.
So as you can see from Lisa's post, FRWTL has quite a few more exercises in it than RKC - specifically lower body drills as mentioned. Another nice thing is that Pavel also goes a bit into power breathing and tension, which aren't really covered in the RKC DVD. As you may know, these two things play a big role in a lot of Pavel's stuff, including KB grinds.
However, there are a few exra things in RKC that aren't in FRWTL. First, it has a different feel because you actually see Pavel doing the drills. As for specifics, there are more details about variations on the military press, it covers the side press, bent press, and the two-hands anyhow. I think RKC does a little better job of laying out how to actually design a routine.
So, overall, I think I got more for my money with FRWTL because it has several more exercises and includes the quick lessons on breathing and tension, and it's only "missing" a few drills. I must say though, that I've gotten quite a bit of information from both DVDs.