The difference? MP1 has +25% MF, MP10 has +250% MF, simple as that. Obviously, that means MP10 has better chance to drop legendary and 6-affix rare per mob. But the time it takes to kill mobs in MP10 is hardly worth it.

Higher MP means higher chance for uber boss to drop Hellfire Ring mats. At MP10, the chance is 100% (with 5 NV stack).

Jewelries and class specific items can now roll ilvl 63 affix.

So you don't believe 625% MF at MP10 actually works, yet you still bother to stack your current MF until 403%? Can you prove your 403% MF actually works?

The fact that you say you "can't" clearly shows how difficult it is to prove that MF actually works. By difficult, I mean you need a very huge sample. You can't just say "I did 10 runs in 1.0.4 and get 1 legendary, I did 10 runs in 1.0.5 and get 1 legendary also". Small sample size doesn't mean shit. If someone says "I did 1000 runs in 1.0.4 and get 100 legendary, I did 1000 runs in 1.0.5 and get 100 legendary also", then his data actually means something. Does anyone have time to do that many runs on PTR? I doubt it.