I have both of these in my living room and I need to choose one in the next 48 hours (but I can't ski them). They fit the same, no issues there. Flip them over and they are identical in every way.
When I twist them I don't notice a significant difference. Will one boot start to become less supportive before the other? I'm plan on wearing them to break trails in southern New England with E-109 or an S-bound 78 skiing flat to rolling terrain (maybe the rare downhill in the apple orchard on the Voile Objective/ Karhu Guide/ Madshus Annum). (note-I did post a related question about the BCX-5 under a previous post- forgive the faux pas if I broke with protocol (I'm still new).
Woodserson was kind enough to comment on the boot before I settled on a ski:
The boots are fine and if you fit and you like them, it would be a good pairing. Just make sure they fit right. I don't think you'd need beefier boots for this combo unless you started to get wider skis and were planning on turning more.