Over the years I've moved my website from b2 to Wordpress to a bespoke PHP solution to Nanoc to Octopress and now to Jekyll.
Octopress is fantastic. It's essentially a pre-configured Jekyll with a very nice set of plugins and a great theme allowing you to get up and running as soon as possible. Which is great for most but perhaps isn't suited to those who like to roll their own. When I set up my Octopress website I spent an awful lot of time hacking away the parts I didn't need. This didn't quite feel right as I knew I should probably be adding to something simpler, not hacking things away from something more complex.
I decided it was time for me to update my website's appearance. Since I wasn't quite happy with my Octopress website, I decided to give Jekyll a go.
I must admit, I was initially confused by Jekyll having installed the Ruby gem and then failing to find a command capable of generating anything. I hit the docs and discovered that Jekyll really doesn't generate anything for you. Indeed you have to create your own directories, configs, theme and posts. This was no Octopress and I was beginning to see which parts were Octopress and which were Jekyll.
I will say that Jekyll really gets out of your way. There's no hand holding what-so-ever (save the docs). It's more like creating a static HTML website then running a command to stitch it together. Once this concept is grasped you just get on with it and enjoy the extra freedom granted.
Jekyll is currently just the tool I was looking for. I love how it gets out of your way and leaves you to set things up pretty much exactly how you want them. You could strip Octopress down this far but then you'd esentally be left Jekyll.
I wouldn't go so far as to say that one is better than the other as they are both entirely different projects with different aims. Fortunately this means choosing between the two is very easy. If you want to build your website from the ground up and be in control of each design choice, use Jekyll. If you want a website that's ready to roll in minutes with a more "convention over configuration" approach, use Octopress.