Conrad Hoffmann:
I believe to have read that using accounting/hibernation is preferrable over rate limiting with fast connections, but I can't seem to find the exact page at the moment.
It is at least in the tor(1) manpage in the details of the AccountingMax option:
If you have bandwidth cost issues, enabling hibernation is preferable to setting a low bandwidth, since it provides users with a collection of fast servers that are up some of the time, which is more useful than a set of slow servers that are always "available".