that is kind of my thinking as well for race wheels. the only real reason i was swaying toward clinchers is that i can ride them all the time. doing everyday riding on tubs where i am would be a costly venture due to the bad roads and all the sh*t in them, but that is another debate all together.

along the same lines as the original post... if the clincher rim weighs about 200g more than the tub rim, would the extra energy required to spin the heavier rim negate the 1.8w loss in rolling resistance? not that i would notice, it's just a thought.