[MonnoncMaxou]

I might be wrong but, isn't the whole point of a bullpup design, such as the TAR-21, the fact that's a more maneuverable, controllable and balanced, weight wise, weapon? Because the guns you've listed will probably end up being front heavy, especially the Echo1 Robinsons Armament XCR-L.

From what you've listed I'd opt for the Masada simply because they should be lighter than the other choices, which will end up being a huge benefit for long milsim games.