I think most of the people that bash on MPC's only bought the first 1. I admit that vol 1 (Rick Hunter) isn't that great with its day glow white and its cheap plastic feel, but they got better as they moved on. I think the last one is the best. (Vol 6)
The first MPC i got was VOL 6 (Jack) and i didn't see that many problems with it. Sure the magnet fast packs dont fit on that great, but either does my 1/60 fast pack. (1/60 fast pack is kinda crappy too, and it doesn't work on all 1/60's, whats up with that? )
The MPC's may be a little loose, but the 1/60s get floppy over time
IMHO they both are kinda lacking....(though not enough to stop me from buying a set of each anyways ) though i like MPC's over 1/60's thats just a personal pref, as pop off leg action really pisses me off....
if you want to add a new valk to your collection, 1/48 is the way to go