Its not always easy to directly compare the two, but generally the M1 is cheaper when you have a small system, and the Omni IIe (or Pro) is cheaper if you gave a fully loaded system. I would start to map out what interfaces and how many serial ports you will need, then compare THAT system with both, if cost is your main factor. Its like anything else, watch out for those add-on's. If you get a fully loaded system, with light, lock control, security, the cost of the board is pretty small compared to the cost of everything else.