was going to say bit of a loaded question...
It
used to be that the "performance" is better on a tubular. lower rolling resistance, smoother, better cornering, lighter...
But like DebW says, its a royal pain in the ar*e (PITA). If goathead is a problem, constant worry of flat(s), clincher may be a better bet.
I'm pretty good at fixing flats and all but its not something I look forward to doing. For that reason, actually the trouble of fixing a sew-up versus clincher, I stay with clinchers.
Clinchers I think are bit cheaper anyway.
just my 1 cent opinion (yes zen

)