Attract Mode really is very powerful. Setup is simple, you can use it almost straight away. It comes with very useful game filtering options to help you make good games lists. The default layouts will be fine for most setups. There is an online visual layout editing tool, you can tweak the layouts provided and/or make some very cool customisations.
To get the best out of it, good to have some experience in (or ability to learn) simple object-oriented programming.
One thing I was worried about with Attract Mode was finding good layouts for CRTs. However, that ultimately isn't a big issue as the layouts it scale to whatever screen resolution you are using. I still found myself tweaking and customising layouts to accommodate things like CRT TV overscan, but it was much less trouble than I initially thought.
I'm also impressed that Attract Mode handles pretty much any media file I throw at it, unlike some other front ends.
LaunchBox is neat, and I use it for my old DOS games n such, but doesn't feel right for arcade cab.