AndyB wrote:If comfort is an issue (and it will be), I'd be wary of dropping from 32 to 23 mm tyres. Whatever, make sure you've done enough on the new lightweight road bike to be sure you can sit on it for the required time - in many ways the more relaxed fit of a typical tourer is better then the normal 'road' bike. Lets face it, at the speeds you will be sustaining for 240 miles, the aerodynamic advantage of the typical low position on road bikes is negligible.
Hm. I think it's rather subjective - there are flipsides to most of those points. Personally I much prefer narrow tyres; IME/O good ones roll quicker and aren't any less comfortable - at least on a light bike; a heavier bike would be a little different. The more upright position of a tourer can be harder on the backside and the back than a flatter position. And if you're moving through the air for a long time, any aerodynamic advantage is worth at least considering (plus long distance doesn't necessarily mean going extremely slowly; my moving average for 200+ mile rides is still 80% of the maximum average I can hit for <30 mile rides).