American Autowire is a "some assembly required" solution. M & H is 100% complete and identical to factory in fit and appearance, it's literally plug and play, just put bulbs and fuses in the sockets and plug in the switches and connectors and it's up and running. You REALLY can't mess anything up, every wire terminates in a factory connector and the harness is custom built for your exact factory configuration, just like the GM parts bins along the assembly line had different harness codes for different option builds.

If you are planning for a concours restoration, consider the appearance. If you plan to add a lot of power accessories and assembly doesn't phase you, then you might want to put together your own harnesses.

M&H is considerably more expensive than AAW. I like that the wires are unbroken between endpoints.