I see you are in the states.
Nistune are local to Australia. Taking the factory ECU and adding a programmable ROM. A great option for your current level of mods.
Vipec (Link) is a New Zealand product (correct?). They are supposed to be great quality products, but any ECU option is only as good as your tuner. If your workshop of choice is confident in tuning them then go for it. The cost could be twice that of the Nistune, but they are about as easy to tune as the other. (From what I am told).
There are a few threads around here on both the Vipec and Nistune. And plenty of experienced tuners who post in this section.
Best of luck in your choice.
I have a Power FC in my (RB20 Powered) car, but if I had the choice to spend the money now and the Vipec was available when I first went to a full A/M ecu, then I would probably have a Vipec in my car.