I've used both BB7's and Hydraulics. I've found that the hydraulics are far better for winter riding. My old BB7's cables would get wet, and then freeze during the coldest commutes, locking them up.

I've never had that problem with the hydraulics. I've never had to anything to maintain the hydraulics, except for replace the pads... My caveat, this is only the 2nd winter on hydraulics. I did have to replace the rear when someone knocked my bike over and snapped off the lever, and wasn't able to locate the a replacement lever for the brand that was OEM.