The alternate models for 7700 and 7701 are excellent. Build them if you can. There's some official "instructions" for 7701 here and 7700 here but they are pretty sparse and a lot of guess work required as it skips a lot of steps. Rest assured they are both great alternate models and I actually prefer them over the originals.

7703 is the least interesting of the lot and 7702 is my favorite in that line. Most likely due to the fact that it's got a more fully formed body than the flat backed others. Enjoy them, they are great! I'm still mourning the end of the line.