dont think there is a reason really. I like the turbo because of its curing advantages over the high build, plus its highbuild also. More like the sikkens primer i've used over the years. This is the first car i'm using spi from top to bottom, so the regular highbuild was the first primer i ever ordered. Used some turbo after that and have just had it in the shop ever since.
The 2k highbuild reminds me a lot of the utech p80 primer i've used in the past. thick and good filling, but you gotta give it time to breathe and cure. Not saying you shouldnt do the same with the turbo. i let all my primer sit a good bit in the sun or run the heat on it in the booth...just extra insurance for me knowing the turbo is a little faster.