First, for around 100$ shipped, I have the Takara Transformers E-hobby Encore Reissue Exclusive Black Megatron.

It have the silencer and "arm rest", plus, it got that nice chrome finish. However, even though it make for a better gun, the brown on the handle/legs bug me. Especially that black gun barrel. Still, he's really great looking and is the most complete.
For 80$ shipped, I have Movie & G1 CH-02 Megatron set

G1 Megs don't have his silencer and "arm rest" here. Instead, we get a very premium voyager DOTM Megs. That "bonus" Megs is really fantastic. Problem is, I already have the regular version. Furthermore, G1 Megs is so... brown here. G1 Megs is supposed to be shiny all over. Here, Megs have a sepia filter applied all over. Still, the colors are balanced.
So, in both versions, both Megs dont have the real colors. Black Megs is more shiny, come with ALL the parts, but is also 20$ more expensive.
The DOTM 2 pack is cheaper AND come with a kick-ass DOTM Megs. However, G1 Megs is "incomplete" and a bit drab looking.
In my eyes, both kits balances each-others out. what would YOU chose?