Call me crazy but... I don't mind the ports. Sure, if you are going to be shooting at a crowded rifle range, you aren't going to make any friends if you aren't considerate to others (I won't pull out my M1895G if I can't put a few tables between me and the other guys; even then, I let them know to wear their ear muffs as it will get a little louder under the shelter). As for muzzle blast, the ports aren't directing the blast back to you, so they don't directly increase noise for the shooter as some make it out to be; it will direct noise out to the side though, so if you are in tight quarters (i.e. thick area, in a valley, under shelter at the range, etc.), you will get some extra echoing coming back to you (or if someone is to the immediate left or right of the muzzle, it will sound EXTREMELY loud to them). As for debris coming out of the ports, I can't speak to that as I haven't seen any issues arise from that yet. I have experienced discomfort from residue coming from the cylinder/barrel gap of revolvers (both large and small bore), so I would expect it does happen to some degree. Of course, you would have to be somewhat on line with the muzzle ports to experience that, I would think.
For me, the reduction in muzzle climb allows me to cycle back on target quicker. I have never had the opportunity to shoot mine against a non-ported version to say that recoil reduction is a big point for me either (of course, to lengthen my stock for me, I put a slip-on limbsaver in place, so recoil is further reduced anyways). And my biggest PRO - it was the only one around that I could find at the time (3 years ago) AND was only $419 OTD (try to touch a new one for that now - back then, that was still some $30 less than Wally World was charging).
And as for your find - $450 for a M1895G with a XS mount and Burris pistol scope? I would be on that deal in a heartbeat. If you honestly tried that rifle (without being dissuaded by all of the Internet postings) and then decided yourself that you didn't like the ports, then you could get Marlin to rebarrel it or sell it off to someone who likes the ports and still be ahead (I have not found a used M1895 or M1895G around here <Georgia> for less than $400 yet, and that's without any accessories on them).
FWIW... YMMV... And my T/C Contender Super 16 .45/70 is ported too - that one DOES make a difference in muzzle climb