My MP-01 is perfect. No chest gap, no sagging over time (and mine's been on display for over a decade). I've had nearly every version of the mold, but the only one I've kept is the first I ever bought - 20th Prime w/ replacement long stacks, and the igear anime head. Greatest toy ever made, and I think it holds up aesthetically more than 10 years later.
But damn, MP-10 is a waste of plastic. If my chest is mistransformed, then it came that way out of the package b/c I never transformed him. And his fingers fall off! I've never had the first issue with MP-01. That thing's a tank. Sure, it's heavy, but it feels substantial and has never had an issue with posing or falling over. Ten feels like a chinese knock-off. And something was bothering me about the face, and now that you say it, it is the eyes. When I compare MP-01 to MP-10, the ONLY pro in Ten's favor is that he fits the current scale. Everything else is a step backwards. If someone made an MP-01 scaled between 01 and Faith Leader, I'd chuck Ten in the river.
I have no love for MP-05, and I don't know if I'll sell mine just because he scales with MP-01, but I'll certainly get the new 3P Apollyon or HasTak 2.0 Megs to be in the proper current MP scale. In fact, if I was only worried about the autobots, I'd use Faith Leader with my MP cars. He's not as large as Mp-10, but he's larger than the cars, and I could make a case that he scales better with them than Mp-10. But, he wouldn't scale well with the seekers, soundwave, quakewave, etc.
But nothing could make me eliminate MP-01 from my collection. I'd sell every other toy or statue I own first.