What is the big deal about this post? It's of or related to bicycle mechanics, and if people are that offended, simply don't post.
6061 is about 30% softer than 7075, assuming a T651 temper, which is very common. However they've both very easy to machine, though 7075 has a tendency to flex a tiny bit, so depending on your surface finish requirements, may require a lighter finish pass. 7075 doesn't have the same corrosion resistance as compared to 6061 though. Hard anodizing parts takes care of the difference in wear characteristics between the two allows though
