-3 point slings: too dificult to quickly get into. the strap that runs along side the gun can get in the way of gun manipulation (caught between reciever and action, reloads, etc. YES, this has happened to me and some of my squadmates. never happened to you after 2.76 million rounds? that's great to hear).
after trying EVERYTHING, I made my own. i have side mounts on the front of my 870 and on my stock.
i bought several 5/32" bungee cords, black, from Ver Sales Inc. (cost me 15 U.S. for a dozen, shipped)
i attached both ends of one to each mount. i then used a regular sling and attached the ends to the bungee cord. VOILA! a sling that will go over the head and left arm to carry up front tactically and also can be slung regularly behind you so you dont scare the public. OPTIONAL: secure bungee cord metal hooks together on mount and excess sling material with 1" black or OD 100mph tape.
i'll admit that this set up has become popular among my department since i've started using it. i've made many of them and shown even more how to make their own. i'ts very simple and versitle. the bungee lets you push the gun away from you a little bit to allow more room to reload and brings it right back to you when done. i love it so much that i even use it on my AR for the same reasons.
ultimately it will be about what YOU like and what works best with your setup. good luck and if you find something original and better, post it. i'm sure others will benefit.