I have both breeds and so did the person I got my SFH (theirs was 2015 GFF stock).
My rocks are barred not buff, but I think still same characteristics. I would chose SFH between the 2. The rocks will be harder to tell apart and they can be kind of bossy. I love having a mix of eye candy in the yard. Both will forage if you are free ranging but I think the SFH are a little better at it. Also they mature earlier and lay a large amount of eggs, and have a good carcass weight and more likely to go broody than the rocks (is a plus for me). They said they lay more than their leghorns where I got mine. Because they are slightly smaller they will consume less feed than rocks as well.
If you are not breeding, try both!

Here I go teaching chicken math!