I got MP01, then skipped MP04 because I didn't want to pay $200 (or $250 if that was the price at Target (I don't remember, but that sounds about right)) for the same toy with a trailer (and no Roller). I skipped MP10, because while it was a whole new mould with trailer and Roller (and Spike), I couldn't justify paying $245 for it. When it came out here for $150 I accepted it and paid it.
MP04 was bigger and had metal, but no Roller (or Spike) and it was about $250. MP10 is smaller and plastic, but it's a $100 cheaper.

For me, Hasbro's MP10 was justified because it was a mould that I didn't already own, and at a cheaper price.
I know I was put off by the smallness at first mostly because of TakaraTOMY's
price. I don't mind if they want to make smaller MPs per se... I just didn't like the original price... MP04 originally retailed for about $200, and MP10 for $245... I personally didn't think it was worth paying that price for a for MP10 - even with Roller and Spike, it was a smaller and fully plastic toy.
The colours do look nicer on metal, but it's not so much that it "needs" to be metal per se, but metal is a more expensive material. If a toy is going to be all plastic, then it ought to be relatively cheaper than a toy that uses die-cast metal parts IMHO. That's why I didn't get into collecting Alternators -- when those toys first came out, they retailed for approx. the same price as Binaltech. For nearly the same price, I might as well just get die cast metal Binaltechs!

So for me it's not just about "metal vs plastic," but rather value for money.
Having said that, I think Hasbro's MP10 is reasonable value and worth paying $150.

To put things in perspective, Hasbro's MP Grimlock sold for about the same price...
that was expensive. But I think it's decent for Optimus Prime.
