I'm not an expert on either. I understand the Holley is a bit easier to self tune. I use a Megasquirt system. I'm happy with it, and I'm not a tuner. I did have a guy tune it and for me it was worth it. I got my system from EFI source.
As for MMX I have been to their shop twice great guys. Dave Webber has been a Mopar performance builder for many years. When my 5.7 based motor dies I plan to replace it from him. The have several I think are good buys. Again these are just my thoughts.
