Technically the SuperSix is the higher ranked of the models, the geometry of the two are very similar, but the SuperSix is the carbon version and Cannondale didn't bother with carbon until it was actually an upgrade, instead they focussed on alu frame, hence they are often regarded as one of, if not the best aluminium bike frame manufacturers. The SuperSix will be an upgrade over the CAAD10 in that it will be lighter and possibly stiffer, it could also help dampen road buzz, having not ridden a SuperSix, I do not know.
With regards, SRAM vs Shimano, tbh, it will come down to feel. SRAM is much lighter at the same price point, but feels very different to use, different shifting mechanisms, a more positive loud shift vs the smooth shimano shift and the hoods feel different, they are a different shape.
TBH, I just changed from Shimano to SRAM (on a Cannondale CAAD9), because SRAM Red is much lighter yet much cheaper than the equivalent Shimano group, I decided that regardless of the shifting style, I would learn to live with it in time in order to save coin (and be able to have a power meter as well as a top tier groupset) and weight (the incredibly low weight means you can run a power meter without a weight penalty vs the other brands groups), turns out there was no need to learn to live with it because IMO the SRAM is amazing.