Originally Posted by
cny-bikeman
Unless the bearings were seriously overtightened the hub is not the proper explanation for the difference. One gear higher is easily more of a difference than the contribution of the entire drivetrain and bearings.
The drag on a "well-maintained" hub its near zero. The drag on a hub with grease that is dried out and chunky can be remarkably high. I've experienced it, as has a co-worker. His hubs were so bad that it was probably an extra 20W of drag. In his case, the wheel wouldn't really spin if freely held. My hubs were in better shape, the bike just felt slow.
So yes, bad hubs can cause exactly the behavior the OP described, and the difference can be significant.
One word of caution though. Angular momentum of the rim plays a huge part in how long a rim takes to spin down. A heavier rim will spin longer than a lighter rim, with the same hubs. This can be hugely misleading when comparing too different wheelsets, for example.