Originally Posted by merlinextraligh

Tubulars: 1) lighter (particularly if you're going with a CF rim)
2) can be ridden flat in extremis (at least moreso than clinchers)
3) subjectively better ride quality
4) arguably a little better cornering grip

Clinchers: 1) a lot cheaper to fix flats
2) a lot less pain in the rear
3) lower rolling resistence
4) more durable braking surfaces. (assuming we're talking CF wheels)

Given your stated use, of training and triathlons, I'd go with clinchers every time. I'd venture to say 95% plus of non sponsered riders train on clinchers. And as for triathlon, rolling resistence of clinchers would be an advantage, and the weight penalty is not as significant in most triathlons