For the record, I also agree with the posters who said that aged teak looks nice-- my assumption is that you're trying to preserve what you see 'now'.

Furthermore, the poster (sorry, I'm on my cell) who noted that the UV will get it either way is also dead on-- doesn't matter whether it's teak or PT- at the end of the day there's no transparent coat that can stop the graying. You'll need to maintain by sanding & recoating. Maybe a thick plastic tablecloth (for those casual days) will help a bit-- like some cover their dining room table all year until Thanksgiving-- that may help a bit too, but make sure the plastic is not torn, or you'll get moisture under there.

Great points folks.