I pushed my router to dd-wrt a while ago. At the time, I liked the UI on dd-wrt better than openWRT. I also noticed some issues on my specific hardware for OpenWRT. How do they stack up?
They're very different beasts.
DD-WRT is a single, monolithic image, similar to a vendor firmware but with more features. What is available tends to be well integrated into the GUI, but if a feature is not available, you're pretty much out of luck (unless you're willing to install software by hand).
OpenWRT, on the other hand, is a package based system: there's a base system and an extensive set of optional packages that you may install. It used to be the case that the OpenWRT GUI was not very good, but it has improved a lot in recent years, and I now find it fairly usable. Of course, not all packages are well integrated with the GUI.
I'd recommend going with OpenWRT. The base system should be reasonably easy to understand, and you'll be able to easily install extra software when you find that you have unusual needs.