Not sure how big they are supposed to be as robots but the vehicle modes for these two look almost in scale for some reason.
Robot modes.
Prime has a nice light-piping eye effect.
I'm impressed with the toy engineering for Megatron; that they made it so that the truck can turn at the connection between the truck and the cargo trailer. As a figure though, I don't really like him that much. I find his arm a bit too long and spindly and I find the shoulders kinda restrictive. Not too bad otherwise. I'm liking Prime a lot however. His size, ease of transformation, and stability in both modes, make him the perfect movie Prime toy to play around with. Some complain about his backpack and paint apps but it's not that big a deal and if you want a movie Prime to play with, this IS the one to get.