I run tubulars. I've seen a lot of tubeless failures, but they almost always can be attributed to bad choices (i.e. a janky conversion, or the wrong tires). If you go tubeless, do it right, with Stan's rims and a widely tested tire. Check this out: http://www.cxmagazine.com/going-tube...ecommendations
If you can go tubular, go tubular. I ran tubeless last season--I couldn't run pressures as I could with tubed clinchers, they were fine for everything but if I had to corner over a ridge (like transitioning from grass to sidewalk) they'd burp, but it only took me some practice sessions and one race to figure out the pressures that worked for me. Burping aside, I felt like the tires were more supple, flexible and grippy even at higher pressures and had less of a "flat" feeling than low-inflated clinchers, so I stuck it out. Although so-so for cross, I liked them for gravel road racing where the disadvantes are less of a big deal, and the feel of them in general encouraged me to convert to road tubeless, which I've been happy with.
I was riding velocity fusion rims, stan's tape & sealant and specialized the captain tubeless ready tires (last season I used the same tires in clincher form).
That said, I think tubulars will give you the best all-around advantages, and are definitely the way to go if you're willing to invest in them. Tubeless is a mixed bag and would probably come down to personal preference over clinchers (probably works better with Stan's rims since their design should make them less likely to burp).