Between the two, Maximus all the way. It's amazingly easy to set up, looks great, is very configurable, and is just completely trouble free.
For me to actually buy software off the net is rare. When my trial ran out, I absolutely had to buy it.
Edit:
Also, I agree with Dazz, Hyperspin is AWESOME. However, it's really great for a select number of games, especially those with themes already. The other emulators are better for running every rom under the sun. However, keep an eye on it. It is constantly updated and has a great community.
If I made a bartop cabinet with limited controls (and therefore limited games), I would run hyperspin without a thought.