That’s why I stuck with 700, plus having 700 wheels on my nice bike isn’t an issue and it wasn’t an issue touring for a month either!
My first touring/cx bike had discs and i decided it was a must for any future touring. The bf and I travelled pretty light anyway, but having discs meant I could descend as fast as I wanted without worrying about stopping power when ladden. I was also thankful for discs when descending Pico Veleta in the coldest/wettest/foggest weather ever – we had to stop half way down for hot chocolate to warm up. I was only able to brake properly because I had discs as I couldn’t feel my fingers! Discs were part of the reason I went for a custom build. I’d say go for it if you can.
I had a power to weight test to see if i could make the clubs race squad. It was interesting to compare my results to the bf – not far off the same power to weight ratio but the watts he was putting out were way over what i was! I would actually say its not so much about the bike unless your current one is very heavy – but about training. Before I started getting coached, i was thinking of lighter bike/getting a power meter but have realised the improvements i’ve made so far and PBs I’ve set are down to training properly, good recovery and eating enough. I’d say good wheels would be a better investment – i want some carbon tubs for racing on!