I've always been a bigger fan of Marvel since I was 12 (I'm 60 now). I always felt their writing were more mature and story lines and continuity were much better than D.C.'s as was their art. My two favorite artists were Jack Kirby and Steve Ditko. I did collect D.C. for awhile but gave up comics in general when new issues went over the $1.25 price point. I still fill an empty space now and then with some of my Marvels but only silver age comics.
I always mark the packages. Having been a comic collector for 50 years I know how easily the P.O. can do damage. I also use two heavy backers in addition to the regular backer board.