For stand hunting in areas where 200yd+ shots are possible, my choice is a MLer hands down. I personally use my Savage ML10II when we hunt IA as it's accuracy and ballistics are greater than any shotgun out there. My TC Omega also has great accuracy and trajectory with Barnes 250g TMZs @ 2115fps MV over 110g BH209. A shotgun and modern sabots can't compare to the trajectory nor accuracy of today's modern MLers, projectiles, and propellants. That said, there's always that advantage to the shotgun of multiple shots and the lack of cleaning.
I've shot slug guns with many diff types of newer sabots and personally found each gun to have a definite preference for the type of ammo it preferred. It can get pretty ridiculous in price while searching for the pet load. With the preferred ammo, I've shot some that were capable of groups in the range of 2" at 100 while others struggled to make 3-4" groups. If you plan to run a 12ga, get ready for some brutal recoil with some of today's sabot loads. Like others have mentioned, the 20 is just as capable with today's loads. Not to mention the recoil is far less.
