I would think the length of time from the Colonies to England would be quite different than the length of time from England to the Colonies. Also, a 1500-ton ship of the line would travel differently than a sloop or frigate. The time of year would make a difference too, and so forth. And as PDR mentioned, the clipper ship wasn't really in use until around 1840 or so.
There's actually a pretty decent article on MSN about different kinds of ships and some maritime history:
http://encarta.msn.com/encyclopedia_761571524_1/Ship.html
I have a book around here somewhere called Colonial American Travel Narratives that I picked up for $1 at a garage sale. It's part of the Penguin Classic library, and if you can find a copy it's worth reading, because it describes all kinds of things from the time period up to around 1800 -- how long it took to travel by horse from this point to that, where the coach would pick you up for a specific departure, that sort of thing.