I'm a follow the #'s sort of guy, but as Marty and Grit have suggested, for the OP, I'd look into your setup first...based on nothing more than reading the posts, I'd want to make sure you had a decent % of weight on your hitch. Would also recommend the Hensley Hitch....an alternative that I had good experience with was the Reese Dual-Cam HP: it eliminated sway so that when a big rig went by, both truck and trailer felt an equivalent push.
If the magic wand was working as well as the crystal ball....and you felt you had to upgrade your rig, I'd suggest a SRW 350/3500...Nothing wrong with duallys and I drove a DRW F350 as a daily driver for a few years, but the SRW's are just a tad more nimble and probably (see the crystal ball issue) perfectly capable for the OP's needs.