I have both wheels, the Fulcrum 5 are by far the better wheel. it is stiffer and spins very well. The balance of the wheel is very good having a couple of plain guage spokes to counter act the weight of the rim joint. The only problem I have had with them is the rim in very tight to get the tyre on you need to blow the tyre up to 100lb plus to get the tyre bead to pop onto the rim so it runs true. The rim joint gives a little thump as you apply the brakes, I just rubbed mine back with a little emery cloth.
However the Mavic is a little softer and will give a softer ride. This could be better if you have a very stiff frame. My mavics have done a couple of thousand miles and the free hub is now loose and needs replacing/bushes replaced. The rims have worn well and the wheels are still true-ish. The rear has a little kick on it, 1 or 2mm. I can live with that.
I am 6 foot and weigh 15 stone.
Cheers
Kris