I would suggest that you go with an O/U. You will find it easier to site, and depending on the make, etc., lighter. After working on both types of guns for many years, there is one thing about these guns that you should know, if you plan to keep this gun a long while and use it a lot.
SxS shotguns tend to work themselves loose after a while under the a/n conditions. As you know, the guns fire from one side to the other, left and right. This torgues the gun left and right. The barrel, however is locked to the frame top and bottom. As the gun gets older, this will cause the headspace between that barrels and frame to open up and become loose. The cheaper (poorer quality) of the gun, the quicker & more pronounced it will become. The best way to tell is to remove the forearm and wiggle the barrel side to side while holding the frame steady and see if there is any play there. I have even seen some new, cheap shotguns doing this.
O/U shotguns on the other hand fire top and bottom, and are secured to the frame top and bottom, so the torquing action has much less effect on those guns. I have rarely seen an O/U shotgun, of reasonable quality, that has shot loose. I have a friend of mine that is very much into trap and skeet shooting and who has used the same Winchester 101 for over 30 year; he figures he has fired as least a half million rounds from that gun, and it's still a tight as when it was bought.
If your intention is to keep this gun for a long while and use it a lot, definately go with the O/U.