The A&K masada is not bad at all. It is harder to service it than the normal M4 and the hopup chamber used to be prone to breaking, especially its slider, but Idk if that's still the case. There is an aftermarket chamber available for it's not a big problem. It is a very solid gun.
I don't really like G&Ps. While they are fine apart from their gears, there is nothing special about them. They are good. The gears were used to be prone to breaking, and they notoriously weren't addressing this issue for years. IDK if they did, I haven't serviced one in years. The shaft of one of the gears was prone to breaking.
A&K m4s are really good both externally and internally. They have good aluminium bodies, not pot metal and SHS or equivalent internals. I would get A&K or Specna Arms if I wanted an M4 and didn't have the money for krytac.