After reviewing the info, I decided that for my upcoming cabinet I wanted the I-PAC / OPTIPAC combo for the total mind-numbing number of inputs allowed. Can't be sorry going that route even though I will never need it.
However, for a second project I am building a control panel standalone for the 'squids' and I chose the Mini-Pac & harness since I won't change it once it is done.
The major difference from an engineering standpoint IMO is the ruggedness of the parts. The I-PAC is certain to last and taste better longer.
For sheer productivity, nothing will beat the Mini-Pac. As Andy says, geared toward OEM cab builders. The small design probably benefitted from some generational lessons. If I was building to sell, I would use it and the pre-made harness to save time.