It all comes down to the person. A manual transmission provides greater control to those adept at driving a manual. I know I wanted nothing less (or more) when driving on snow and ice. On the other hand, if you take the average auto driver and throw them behind the wheel of a manual, I doubt they'll have more control. Almost certainly the opposite.

The same is true of a fixed gear.

As for fixed on ice, baca, you're making the assumption that the changing weight distribution is more detrimental than the loss of positive engagement with the road surface both forward and backwards. I know of no proof or disproof of this though I do know personally that I don't find it adversly impacts my riding.

As for the brake failure thing, I wouldn't sweat it too much. Not everything has a fail-safe backup. What do you do when your front tire blows out at speed? Have you figured out how you'll unclip and dismount in time to catch yourself? What if your wheel collapses? And so on. I would however be more concerned about no control over the back end when braking. I know people do run SS with just a front and that may be good most of the time, but I also know that I frequently use two wheel control in order to effectively scrub speed while maneuvering.

-Trevor, who freewheeled over some ice last night only to throw the rear into a 180 degree slide at the end (but seated and upright the whole time--I love winter!)