You can get a more powerful end game character with a dual, but I'd take the multi for ease of playing throughout and you can pick a short race for the saving throw and racial thieving bonuses. I'd also take the F/T over the Swash for its increased combat ability and the ability to backstab.
If you are going to ToB, then I think multi results in a more powerful endgame character. The thief gets use any item, and some of the epic thief traps are quite powerful. The fighter side will also provide some of the fighter epic talents. That is a ways off, but I also like multis for ease of play, as ryuken87 already mentioned.