not apples to apples... imo you should be looking at the stinger pimpxs vs the terminator.
The pimpxs has way more capabilities than the terminator but the holley will come with a new harness.
The MS will require the purchase of a seperate WB, I suggest a spartan2
both are easy to learn.
I am biased toward MS although I have tuned many ems systems. they all have pro and cons, if you make a wiring mistake with the holley and loose an input ect, it is a paperweight... the ms can be opened and repaired, this to most users is not a reason to buy one over the other.