The Scarpa Rebel Ultra and Rebel Pro are virtually identical boots. They share the same last, fit, insulation and, best as I can tell, the whole lower 2/3 of the boot – basically the part that encases your foot. Both boots have front and rear crampon bails, Gore-Tex waterproof linings and carbon-fibre insoles. They differ drastically in their upper construction. While the Pro has a traditional-style cuff with two lace hooks, the Ultra has a ‘floating’ cuff arrangement with the two lace hooks situated on two ‘detached’ wings that wrap around the ankle. The Ultra additionally has an integrated gaiter with two huge pull-tabs, which are rather necessary to pull the boot on.
For their 2013 release dates, the boots also featured different soles: the Pro used Vibram’s Mulaz S outsole, while the Ultra got the Vibram TT Lite. (Though for 2014, both boots are specced with the Mulaz S.)
The TT Lite has slightly shallower lugs, and a marginally different lug arrangement. There is a prominent ‘climbing zone’ at the toe, and along the leading inside edge. The rubber compound appears to be as sticky as the Pro’s similar Mulaz S. The Mulaz S, currently shod on the Pro and coming to the Ultra in Spring 2014, is, at first glance, a much ‘beefier’ sole. The lugs are deeper and the pattern is more aggressive, with more prominent braking and omni-directional traction lugs. There is also a large ‘climbing zone’ at the toe and leading inside edge.
Showing the slight difference in lug depths between the Ultra (in the back, orange upper) to the Pro (in front, black upper). The rubber compounds also appear to be slightly different (notice the shine of the TT Lite sole on the Pro vs the matte, more foamy look of the Ultra’s Mulaz S).
Both boots have front and rear crampon bails, and the same amount of cushioning. In a size 43, the Ultra weighs 766 grams, compared to 761 for the Pro. The difference is negligible. Whatever magic Scarpa has played with the carbon-fibre insole is present in both boots: a rigid platform for climbing and front-pointing that somehow retains flexibility when walking. It is truly amazing and something that’s hard to describe until you experience it. Just imagine that these boots walk like a stiff, slightly bulkier trail runner, climb rock like a stiff ankle-top tradshoe, and scoot up ice and mixed like a heavier, warmer fruit-boot. Yes, they really are that good.
So, which to choose? As I am fortunate enough to own both of these boots, here’s what I did: I sized the Ultra at 43.5 to accommodate thicker winter socks and the Pro at 43 for use with light- to mid-weight socks in the summer/fall. The flexible ankle of the Ultra makes it a better ice and mixed boot; it is easier to twist and turn your ankle around a front point in the Ultra than in the Pro. The Pro, on the other hand, offers slightly better support laterally around the ankle, making it a better rock boot, i.e. one in which you stand more over the toes and require less ankle flex. Also, due to the integrated gaiter, the Ultra is ever-the-slightest warmer and better for post-holing during those thigh-deep-snow slogs. Basically, I chose the Ultra as a warmer-day ice and mixed boot (I’m happy in them to -10C or so) and the Pro as a three-season-plus alpine boot. Keep in mind that both will do either equally well. As I wrote above, the Ultra is somewhat better at higher-grade ice and mixed where advanced moves are more common while the Pro will be better at edging on rock and will have better ankle support on slabby terrain. This is why I sized them differently: the Ultra to accommodate a slightly thicker sock, with room for kicking into ice; and the Pro for use with a light- to mid-weight sock for those Rockies alpine days where you really need to know where your toes are at. I hope all of this helps with your choice, somehow. If you do come up with some questions I haven’t answered, please do let me know and I’ll address them to the best of my ability!
Note: Scarpa North America provided The Alpine Start with the Rebel Pro however this is no way influences our opinion of the product.