I have 4 G3’s. I have 2 TM’s (SAS and SBD), 1 CA (M41) and a JG (G3A3 with real wood kit). I like all of them!!! The longer the barrel the more you have to worry about the “creaks”. The “family” can be seen here:
viewtopic.php?f=5&t=7946&start=315 The pics of the A3 are on the next page.
I can’t say that I have ever really had issues with any of them. I got them all used and the gear boxes have been opened on all of them. Will they last as long after they have been opened………… Who knows?
I don’t think you would have any issues with the MC51. It would make a great CQB gun. I like the TM’s over my CA because of the “heft” of the CA metal body. BUT the CA is my main CQB gun due to the RIS. The nice thing about the G3 is the changeability of the “lower” body. If you can find another lower you can set one up for CQB and one for higher FPS outdoor games. You can change the unit over in about 2 minutes (if that long). I pull 1 pin separate the body and slide the new lower on. It’s a little more involves on guns wired to the front but not much. I like full stocks myself.
I haven’t been airsofting as long as many on the boards but the one thing I have learned, Buy what looks good to you and is in your price range. Do you want plastic or metal? You have options for each. If you get a decent AEG you can fix what breaks. There are many brands out there and somebody will have bad things to say about any of them. Everyone will have there favorite mfg’s and yes on some guns it might make a difference (IE harder to disassemble, bad wire routing, ect).
Good luck with your choice.
OGF