I think this is like asking if a Ford is better than a Chevy-you will get all sorts of opinions.
I am a big Holley EFI fan (probably because I am using one), and I did a LOT of analyzing before I bought one-none of these Systems are what I would call "cheap"-

My reasoning has more to do with the ease of use, available support (Holley expects that whoever you purchase their product from to provide Technical/Start up support-that was big for me), and, there are remote Tuners available to help (I think there are also remote tuners available for FAST too)-the fact that Holley offers a few different ECU's (read cheaper/fewer inputs/outputs) gives you a choice-

I chose the Dominator due to the fact that I am running a 4L80E and needed something to control my electronic Transmission (you can't do that with an HP)-to do the same with the FAST, you have to run a piggyback, although I believe they will (and are) catching up-its' all in one Box with the Holley-

Also the Dominator offers a LOT of inputs/outputs-I didn't think that was a big deal at first, then I realized that (for instance) I could do away with an electric Fan controller (you can set the Dominator to turn on/off the Fan at whatever Temp you choose), and, I am running things like my paddle shifter through it, along with an engine shut-off if the Oil Pressure/Coolant Temperature go over limits that I set (and lots more)-you will find all sorts of reasons to use them-

I would look hard at the Holley HP-it's definitely cheaper, and if you don't need as many inputs/outputs (think hard!), or need to control an electronic Transmission, it could save you a reasonable amount-