Ghost requires installation and tinkering (plugins, themes, etc). Silvrback is designed to give you something that looks great and doesn't take up your time. I believe that people shouldn't spend any time building a personal blog. You should spend that time on your products instead.

I could be wrong, but I think Silvrback probably has much better syntax highlighting than Ghost (do they have it at all?) and it gives you a bio page so you can consolidate your brand.