I've used/had/driven Hi Spec brakes on some cars, as well as a few wilwood.
There really isn't anything between them, other than you may not have a year long wait for your two week order like Hi Spec used to be, said to be much better now though.
I was however mortified to see Geoff(Hi Spec) skimming a set of discs in the lathe by skimming one side then taking out turning round and doing the other side, instead of back skimming.
My first experience was a cossie kit on a normal 2l sierra, he fitted them after reconing the calipers, the inner edge of the outer pad nearly broke all the way the bell it was on, as when the initial material was worn away just 100 miles later, the outer pad was hitting the bolts holding disc and bell together.
I had to take to pads off, and grind away the inner edges a bit to clear.
It was while doing this I noticed that 3 or the 4 bleed nipples were leaking slightly.
I tightened these ,(although they did seem tight enough to start with), still leaked.
In the end took them to a enginnering place as though the bleeed screw seat was damaged, took apart and found to have blasting grit in them.
tabetha