If you have a number of carts and like changing games often, then a single slot will become a pain in the ass. Get the 4 slot, and make sure the cab supports it.(if your using a cab)
A single slot will work in any jamma cab.
I have selected 4-slot. MOTW and KOF98 are must site in the cab, and I don't really like to open coin door, control panel all the time. Thank you guys for all information. I enjoy my neo geo life so much.