Re: 75 Hornady's vs 77 smk's?
The 77's should have a lower BC because of the Ogive. You should expect a bit more wind drift and drop at distance. If you're talking about stabilization, if the 75 stabilizes, the 77 will too.
Other than that, Sierra's just generally cost more than Hornday's. Whether it has to do with materials, or consistency, or just paying for the name...maybe a little of everything.