Cetol
I bet your question gets asked a lot. Everyone has their own answer. Here's mine: Varnish done right looks much better than Cetol. Most varnishes will require very careful prep and about 7 coats. It won't last as long as Cetol before you either have to strip it or carefully feather on another coat or two if you haven't waited too long. Cetol, on the other hand, is much easier to use, lasts longer, is much easier to maintain, but doesn't look as good as varnish. Having said that, I have been using Cetol for the past 10 years and will continue to use it forever. Cetol is the best product for people who like to sail a lot and want their boats to look pretty good. Varnish is for people who are going to have less time to sail, but will have better looking teak on their boats. Take your pick.