I have them all (see the Manix wheel post) and I think it's never a bad idea to have a matched set in SE and PE. I use the serrated blade as a defensive carry, a rope cutter, weed slasher, and branch trimmer. The plain edge is used for everything else.
The se is generally carried in places where I can't have a gun or when I'm intentionally going to be doing the stuff mentioned above.
To answer your question: the PE gets carried the most but the SE gets used the hardest.