I use 9K - that works best for me - the reason why I mention this is to highlight the need for each user to test their network, because the best settings will differ from one network to the next.
Something worth noting also, is that the "best setting" is also dictated by the nature of the data being used, if you're testing with large files (which is really where jumbo frame makes sense), but the normal day to day data is smaller files, you could be "shooting yourself in the foot"