My most recent tub flat was last week. I train and race on tubs, so I have a good sense of their durability. In urban NY, you can expect to flat. I flatted a 25mm Conti Sprinter Gatorskin last Tuesday after a piece of green glass dug a burrow through the tread and the breakers. It was a front puncture, and it expressed itself in a fast downhill bend, so +1000 for tubular safety. I'd be typing this from my hospital bed or not at all if that had been a clincher.
My routes are an antique road show of busted beer bottles, torn cans, shattered automotive anatomy, displaced tarmac nuggets, and occasional contributions from hypodermic enthusiasts. In other words, crap. I rode Veloflex Criteriums for years in West Florida on vacant rural roads and suffered only one puncture that leaked slowly enough to ride home.
In general, you will *puncture* flat a tubular as often as you puncture flat clinchers. Your road conditions will determine that, so you probably have a good feel for your roads and propensity to puncture tubs if you are riding significant miles on a comparably protected (corespun? vectran?) clincher.
Pinch flats will occur far less frequently, with or without a latex-tubed tub. Both are excellent for running low pressure with assurance, but the latex will have the edge if you want to try Roubaix-style pressures below 5.5 bar.
Broadly, I think that tubulars are not a WW option unless you are building a pretty high-end carbon tubular wheelset and using more puncture-prone race tubs. GP4000s on Kinlin XR200s with Sapim CX-Rays and Tune or Extralight hubs will be extremely WW if that is your only goal. My Sprinter Gatorskins weigh 325g each (not counting about 60g of glue!), and I'm running them on 32 hole Nemesis Rims with Aerolite spokes and King R45 hubs. It's not a WW setup, it's a real world tubular setup for races and roads that include crap and monster potholes. A GP4000s and a latex tube could ride just fine and weigh 260-270g combined. For WW purposes, clinchers may be your best bet at reasonable budget levels. For feel, read on.
"Tubular feel" is 90% tire pressure. Because tubs -even butyl- can run such low pressures without pinch flatting, they can be inflated (or deflated) to feel extremely supple. That last 10% is a function of casing thickness, tpi, latex casing, latex tube, and tire volume. Even huge men like Boonen and Cancellara can run 4.5-6 bar at Roubaix on latex/latex 27mm FMBs because the pinch resistance of that setup is stellar.
I run the 25mm Sprinter Gartorskin for all applications in NY and use 4.5 bar front and 5 bar rear over my local Bosnian roads. I weigh 61kg and I've never had a pinch flat on this arrangement. My ti bike rides like a Cadillac on this setup.
Now, about those punctures. I am trialling Conti Revo sealant in both tires. I had purchased this new sealant option with a view to installing it after the first puncture rather than filling the tires immediately. It came out in the last year, and it doesn't contain ammonia like Stan's and some others. Conti endorses it for their tires and won't void warranties if you use it in tubs, and it seems like an option that could be safe for latex-tubed tubs as well. I removed my valve cores to install it, but Conti says it can be piped though presta stems without congesting the mechanism if your cores can't be removed. Personally, I wouldn't tempt fate, but it's nice to know the possibility exists. I contacted Conti and they advised 60ml per tire.
So far, it resolutely sealed the 2mm hole and has returned me to the road. I'm curious to see how it responds to a real-time puncture on the road. Since I haven't seen any 'net evaluations of the product by tubular riders, I plan to post a full review of my experience with Revo as a tubular option once I have a good feel for its qualities. I know many here would like to run tubs full time, would take the plunge if flats were less likely, and would love to have a good sealant option.