Diecast metal

[GoktimusPrime]

People keep comparing alt and blt because of the diecast but isn't it the actual paint that makes the blt look nicer I bet you could make the alts look just as nice with the same paint and you wouldn't know the difference...

Which is what TakaraTOMY did with Alternity and the MP Cars (that paint w/ the nice glossy finish). Alternators definitely could've looked nicer if Hasbro had bothered to slap some paints on them, or selected better plastic colours. But unfortunately, Hasbro simply didn't do this for Alternators.

Because of the following:
1. The metal give a deeper shine to the toy which equals higher grade of quality, As I pointed, Wheeljack mp felt lack of paint on White plastic.

But if they had applied a glossy pearl white coat of paint on Wheeljack, then would it still matter to you that it was painted plastic and not metal? Look at the paint job on say MP Streak, that looks pretty damn good IMO.

2. The rubber tytes debate is because toy car collectors DO NOT collect toy cars with plastic wheels, is a slap to them, hence the follow suit here in a Masterpiece line, not for other transformers though.

That's still a very subjective standard that you're using there. It depends on whether or not you view Masterpieces as scale model cars first and transformable action figures second. This is more something that BT/Alternators marketed itself as; and as I understand it, one reason why Hasbro had to name Alternators Meister "Meister" instead of Autobot Jazz, was because the toy fell under the miniature car trademark instead of action figure trademark, and they couldn't even use the word "Jazz" at all in a toy car, even with "Autobot" stuck in front of it (probably because of the Honda Jazz?). Subsequent Jazz toys (e.g. Movie, Animated, RtS etc.) did not have this problem, as they fell under the jurisdiction of action figures, and Hasbro were able to call them "Autobot Jazz."

If you personally view MPs as replica vehicles first, that's fine, but not everybody necessarily holds them to that same standard. I personally see them as action figures first. Binaltechs, Alternators and Alternities are more of what I consider to be replica vehicle-formers; BTs/ALTs go into insane details with seats, steering wheels, dashboards, gear sticks, park brakes, bonnet, engine, boot, steering et al. MPs don't do that, as their engineering is more focused on translating cartoon models into fun toys (making the 'impossible' possible). BTs/ALTs aren't at all constrained by this; the robots just need to bear a recognisable resemblance to the characters, but otherwise they have a far greater range of freedom in terms of design and engineering.