I just went through this raging inner debate recently. The main deciding factors for me were the original frame design. My frame is an older hardtail designed around 70mm fork. It also has a 71.5* headtube and has always been just a little fast for me. It is a telepathic singletracker, but can be more of a handful for me on downhills.
Given several years of decreased riding, and growing older and getting worried about crashing, my downhilling has really suffered. I wanted a new fork that would 1) upgrade my 99sx ti to more modern suspension; 2) slacken my head tube JUST enough to give me more stability but NOT turn the bike into a couch.
In talking to Tom Rogers at the Soul Rider forum at
www.bikemag.com (he is a former Manitou R&D engineer. See this thread:
http://forum.bikemag.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=16;t=000054)
he informed me that the BLACKS are designed around 'free riding' and are designed around a taller tire size than the Skarebs which are designed around typical XC tire sizes. Regardless of your definitions for free ride vs XC, it means that the BLACKS are 8mm taller than a comparable Skareb because of the tire design issue.
His suggestion was to go with a Black 80 because it would slacken my head tube out just enough to give me more stability without compromising the good handling of the bike.
So my choices were, in order of how they might 'slow' down my bike were
-Skareb 80
-Black 80
-Skareb 100
-Black 100
I went with the Black 80 SPV ( if you look hard enough you can find some Black Elite Airs from 2002 that are 80mm also)
I've got 2 rides on it so far, and it is working just as he said it would. The handling is less twitchy, and feels much like my last bike which was had a 71* head tube. It requires me to 'push' more and muscle more on turns and singletrack, but it is so much more stable that I am flying again.
The fork is sweet too. I still have a ton of dialing in to do with choosing the air pressure, the SPV pressure, spring, rebound, etc. but man, it rides nice.
I am not so sold on the SPV thing, and sort of wish I'd bought a used Black Elite Air 80mm I'd seen in the classified for half of what I paid for the Black SPV. But overall I am very pleased.
So anyway, be aware of the ride height issue when choosing between Blacks and Skarebs.