Those two matches have been around for a bit now, I think. I had them on a History of Midnight Express v. Rock & Roll Express comp.
I remembered LOVING the Fantastics/Midnight Express feud growing up and back then thought that feud was better. Having watched more recently, and seeing their WCCW matches as well, I go with the RnR-Midnights feud. I just think, overall, it has the history and the matches are still great. A lot of the stuff done in the feud with the Fantastics was done first with the Rock & Rolls. I actually got the chance to see a Rock & Roll Express vs. Midnight Express match main eventing a show in Galveston TX when I was visiting family. It was fantastic, even with a small crowd.