There are two types of "MULTICADE" boards. There are the single board solutions (39-in-1, 48-in-1, 60-in-1, and the new 19-in-1 horizontal) and there are multi-board solutions (111-in-1, 170-in-1, 465-in-1, and 1011-in-1).
The single board solutions are essentially a small computer built on to a single board running a very old version of MAME. Being a single board solutions it is very slick and quick to boot. No one is sure what OS it runs nor what "CPU" it runs...it functions essentially as a JAMMA board that can play multiple games via a menu.
The multi board solutions are actual MINI-PC's...complete with Celeron CPU, heatsink/fan unit, memory stick (or two), and for storage they use either a compact flash card or even (in the case of the 1000-in-1) a hard drive. These units are actual PC's sandwiched on to a JAMMA converter board. They use a newer version of MAME than the single card solutions, but being an actual computer there is a boot time, plus they are about as reliable as your every day computer.
MAME is MUCH more configurable...and flexible. But it also take a lot of work to get going "right". That said, it is much more rewarding when you are done than dropping in a MAME box (essentially what the PC-based multigame boards are).