Go to
www.sheldonbrown.com and look for his articles about the differences between tubular and clincher tires. Sheldon and Jobst Brandt are highly regarded experts on cycling equipment in general, and all things wheel-related, in particular.
I'll paraphrase what I've read there. The mystique of the tubular tire's superiority to the clincher is something that's carried over from the old days when all clincher tires were heavy, wire-beaded things. Today's kevlar-beaded clinchers are much lighter. The combination of a tire/wheel and/or tire/tube/wheel will still show a slight weight advantage to the tubular tire. However, if you are inclined to carry a spare tubular in the event of a flat, as opposed to a spare tube for your clincher, you will have fully negated the weight advantage.
As for rolling resistance, there are high-quality clincher tires that are actually superior to tubular tires. If I understand this correctly, because clincher tires tend to be more eliptical in shape, they tend to have a smaller contact patch. Granted, you can generally get a higher psi with a tubular tire. But Mr. Brown argues that the optimal psi for a tubular or a clincher is about the same ... so no advantage there, either.
I've read many posts in Slowtwitch where people talk about a big advantage with tubular tires being that you don't get pinch flats. I've ridden 150,000 miles on clinchers over the last dozen years. I've NEVER had a pinch flat. NEVER! Pinch flats generally happen when you run tires at low pressure and impact something very hard. Mountain bike riders get lots of pinch flats 'cuz they run tires at 30 psi or less. You're not gonna get pinch flats on a clincher at 110 to 120 psi which is the most common inflation range.
Tubular proponents will argue that you can ride a ways on a flat clincher. So what? How far are you gonna ride it? This is an advantage for the pros who can keep up with the peloton while they await the arrival of neutral service or a team car. What advantage is there to the average joe? None! If you've gotta fix a flat, you've gotta fix a flat. Period. I can put a new tube in a clincher and be rolling in 3 to 5 minutes. Or, I can put sealant in ... just like you can with a tubular.
Now consider the price. HUGE advantage to clinchers. HUGE advantage.
So ... weigh what you read carefully. Tubulars have a lot of mystique and myth. The days where they offered a meaningful advantage were in the past.
Bob C.