i cant say much for the mossy or the H&R cause i havent used either for shooting slugs. and havent shot a 20 ga. in my life, but they will do the same job as a 12 ga.

the condor i can say is a pretty good gun. couple down sides of it that im not to fond of. 1) fires he bottom barrel first (and there is no way to change that) 2) doesnt eject the spent rounds (you get crazy shooting alot of rounds in a short time those shells get REAL HOT)