I ride all of my vintage Cannondale ST bikes with 630 (27") wheelsets.

My bikes are 27" frames (~68.5cm) and I think that 622 (700c) wheelsets make them look more ridiculously out of proportion than they really are. Additionally, I think all the inanity in cycling that 622 is "new" and "better" and 630 is "old" is freakin' idiotic. I ride 630 as a protest vote as much as anything. I can get any type of tire I need in 630. However, it is funny how many people try to encourage me to actually NOT have 630 bikes. The usual argument is tire availability, followed closely by it being "old." What is really funny is usually these same people have a 584 bike (650B) that they insist is "best" for touring. I try to explain that no wheelset is best for all frame sizes large and small, for whatever intended application. What might make 584 appeal to someone on a 57cm frame is not the same as 584 wheelset on a 49cm or a 68cm bike. What really cracks me up is how I'll have my half of the conversation identifying the size as 584, and they'll typically respond with 650B. Tells me what I already knew, that their investment in 584 is as much emotional in validating some sense of being an esoteric european touring size. I'm serious. Start calling it 584 and watch 'em twitch. It's funny.

There is no one "best" road tire for a Fiat 500 and a Cadillac. There is no "best" light truck tire for plain jane 2wd toyota mini truck and a Ford F350 dualie. C'mon people, stop reading Jan's blather in between reprinted images of Robeur's art. Think for yourselves.

All that being said if you think you can tell the difference between the marginal 4mm difference in radius from the 630 to the 622 you're kidding yourself. You're noticing the difference in tire construction (tpi), the crafstmanship of the wheel build, anything but you're NOT noticing any fundamental difference in how the wheels roll. You might be noticing the differences in gain ratios.

If you really want to compare, compare identical tires/tubes and wheelbuilds (have Peter White build you up a set of Phil Wood/Velocity wheels in 630 and 622 with identical spokes). You won't notice the difference. If you think you can, I'd say you're kidding yourself. Then again, maybe I'm wrong.