I did a search and read the posts on 650 vs 700. I can see the reasoning in smaller frame sizes. However, some 56 and 57 frame sizes offer both wheel sizes. WHY? Also, Dan stated several months ago he may write up his opinion on this matter. Is it on the site? FWIW, I am 6-0 and ride a 56/56 c-c road frame and am looking for a tri bike.
Aside from the small frame sizes (and only on the super-small road geometry frame sizes), 650 wheels are more about marketing than function. Sure back in the early days they were experimenting with smaller front wheels and larger rears, and some thought that the smaller wheels gave an aerodynamic advantage over the large wheel sizes (largely debunked) - but for tri bikes over 52/54cm, there’s no logical reason not to run 700’s.
I can also agree with Khai. The only real advantage that 650c wheels have over 700c wheels is a quicker acceleration. While this might be good in a sprint race, I wouldn’t recommend using 650’s in anything longer. There’s also more diversity with 700c wheels: easier to find tubes, tires, tubulars, spokes, etc.
The reason for 650 wheels is to be able to get the front end low enough to get a good aero position. I am 5’ 8" and I have very short legs. There is no way I could get low enough with 700 c wheels.
At six feet tall, you wouldn’t have that problem. 650 wheels are a pain since the vast majority of wheels are available only in 700. I would use 700 wheels if I could, but for my build, there is just no way.