About the aero frames vs not so aero..
I think the time trial bikes are designed that way because the 'aero position' is really only effective in speeds above about 25 mph. On a TDF climbing leg, you're probably not doing that a lot of the time so it becomes less important. Then the weight becomes more of an issue as well as things breaking. However, on a TT you may be doing 30-35 the majority of the race.
**I think**