^Where's psu, case, hard drive? You're leaving out some of the costs...
With both of those mobos, you'd need a better video card, as well.
The $45 "system" mentioned above is a motherboard only and does not include case hard drive etc. The OP stated he was going to use a 2GB flash drive for storage (no HD needed) and for MAME you do not need a special video card (unless using arcade monitor), on-board video will work just fine.