i had a bike with sewups/tubulars 25 years ago. in those days, sewups were way lighter than any clinchers, much more narrow, and just generally cooler. that is no longer true. i wouldn't recommend them for road riding, because they are more expensive, difficult to put on (you gotta use glue) and patching them is, well, interesting. somewhere i think i still have the old patch kit, with the needle and thread.
a week ago i saw someone had left a bike wheel on the curb near my house, and it was a mavic tubular rim laced to some crappy hub with a frozen axle. i sort of regret leaving it there, but really, what am i going to do with one 36-hole tubular rim? garage is getting kinda full...