This might help.
I have just bought a M14 after quite a bit of research and feedback from an experienced downwinder and others. I have no experience of the other boards and am just starting to use the M14 so can't give you direct feedback.
in my research, obviously the SIC and M14 are full on downwinders .....the glide is more a race/downwinder cross. On the flat I guess the Glide will be fastest....it seems to do fine on downwinders too but need to watch the nose a bit.
www.seabreeze.com.au/forums/Stand-Up-Paddle/Review/New-Downwinder/On the sea and in downwind conditions the Bullet is the fastest of them all.......that is why the vast majority of folk use them on the Molokai race. You will pay more and it is a bit more tippy than the M14. The 2014 M14 has had its hull tweaked to a more flatter rocker....bit faster and better glides so I am told but I wouldn't be able to confirm the extra speed etc as I have no prior experience.
i chose the M14 - the feedback is that it is more user friendly for an intermediate than the bullet and handles rough water very well for someone of my ability. It also has a rep of being the most surfy......nice if you come from a surf sup background. At this stage all I can confirm is that it is really stable in rougher water and appears to pick up bumps nicely. The finish is great and they of course look magic.....surprisingly light and the toughest out of the three. The only downside I can see is the handle isn't the wrap around ergo type like the Naish.....but it is a deep handle And not an issue if you have an okay walk to the water.
All three boards are top notch I reckon so you can't go wrong