This is the most interesting comparison, clincher to clincher. The 27" tire is 5mm wider, roughly 1/4". That combination is 8oz heavier, half a pound.

rj doesn't say here but we can assume the hubs and QR skewers are similar. The rims would be different, though if the 27" rim was the Yellow Label I recall that as reasonably light. It might be wider than the the 700c rim though, and thus heavier. The tire probably accounts for most of the extra weight, I'd guess.

The tubular wins on weight hands down.

It also occurred to me that in the original comparison the freewheels could have made a big difference if the World Tour-equiped wheel was meant for carrying a load and thus had bigger cogs.

Thanks for the weight measurements!