Ubuntu and CrunchBang are very similar to each other because CrunchBang is based off of Ubuntu. They each have their benefits and problems.
Why CrunchBang?
CrunchBang is a Debian GNU/Linux based distribution offering a great blend of speed, style and substance. Using the nimble Openbox window manager, it is highly customisable and provides a modern, full-featured GNU/Linux system without sacrificing performance.
If you are looking for a fast distro I advise using CrunchBang, it is built for speed. But it isn't the best when talking about user friendly, one of its downsides. When I got an old tower, it had little RAM. So I decided to try out Ubuntu on it, it lagged a lot and I need to find a alternative. I found CrunchBang, it was a great fit. It ran great and it did exactly what I wanted it for. So if you are looking for a fast distro pick CrunchBang.
Why Ubuntu?
Ubuntu is a distro that is built for the user. Making it easy for the user to use it, much like Windows. If you are looking for an alternative to Windows and want a friendly UI I advise Ubuntu. But remember you must have a decent computer to run Ubuntu.
It all comes down to what works for you. If you are looking for speed then choose CrunchBang. If you want a user friendly system pick Ubuntu. Hope this helped you decision when choosing either one.