My vote was to play it out. But let me throw out the Mac diatribe everytime this situation comes into play at a GS. He makes some good points, but in the end I think he's all wet.
He says when you get that far into a match both players are not at their best. They are tired and usually the quality of tennis isn't very good. He says it's just not good tennis to watch. Two players tiredly dragging their carcasses all over the court making lots of mistakes. He feels a 5th set tiebreak would let these guys see a light at the end of the tunnel and let it all hang out for that last bit of real estate. For the viewer a 5th set tie break should give the best theater.
That's Mac's take.
My take is that I've seen both 5th sets played out and, at the US Open, 5th set tie breaks. I don't see the difference, and I don't see the huge drop off in quality. I think the best fit player should win that kind of match and that won't be told in a tiebreak.