Originally Posted by mazdaspeed

Frankly, none of those tire options stack up to a good 700c. They're way heavier, have worse compounds for grip, and don't roll as well. Comparing a tan-wall 27" tire to a high TPI 700c racing tire is insane.

The rims thing is debatable, but once again, ultimately 700c has better options.

If you're tooting around the neighborhood or MUP on your 10 speed bike with 27" tires you won't notice any difference, but get into a more competitive situation and I daresay that the heavier wheel/tire combo and less grip / more rolling resistance will be an issue.

I also agree that this thread is mostly BS and that the difference is probably negligible for most casual riders.