The difference is about 4mm if I recall correctly, it doesn't make much difference other than opening up your tire selections. Usually the stock brakes will just need a minor adjustment. I have 27x 1-1/8's on my Miyata 610, which are roughly equivalent to a 32c width tire. On my Nishkiki International (27 to 700c 'conversion'), I've fit 700x35c's without an issue.