I had the same question you did. I went with nistune.
I am running Nistune on my RB25 and I love the product. I Baught a Z32 ECU and sent it to Andy at Autovaughn Performance in Tennassee. Great guy and he answered all my questions About Nistune. From the beginning i couldnt see paying $2000 for AEM EMS or $1200 for PFC especially cause not one tuning shop 200 miles around me had ever tuned a RB25 before let alone used PFC before. So then My only choices were Nistune or Megasquirt. I didnt want to make the megasquirt board and buy all the coils and crank triggers and what not so i went with Nistune.
http://www.autovaughnperformance.com/
Reasons to go with Nistune. 1-You can go to any junkyard and get a z32 ecu anywhere from $40-$100 I picked mine up for $50. YOU CAN GET ANY Z32 ECU! IT DOES NOT HAVE TO BE FROM A TT OR A STANDARD CAR! It dosent matter because you take the read only memory chip out and install the nistune type 2 chip. Try to get a ecu from a 1990-1994 that are 8 bit ecu's, they are a little more nistune freindly. 1995-1996 ecu's are 16 bit and are a little more advanced and need a type 3 more exspensive board.
Posatives to having a Z32 ECU - Keeps the RB25's VVC.
Negatives are that you have to switch around a few wires to make it work. No big deal
So I made a call to Andy and i needed a wideband and Nistune supports a ton of them. I opted for the Innovate LC-1. At $229 you cant beat the price and it was rated one of the most acurate widebands and most of all Nistune can see it in their program.
From Autovaughn for just the Nistune product for everything it came to $495 and for the package for him to install it and make sure everything works it was $505 so sent him the ECU for him to install the chip. For $10 more it saved me the time and agravation. So that came with chip installed consult cable and tuning lisence software.
I have been tuning it myself gradually. Im running 13lbs of boost on the stock turbo, with Afr's at 11.8 under boost.
So in the end $505 + $229+ $50= $784. it was still cheaper than PFC and i can tune it from my Lap Top unlike PFC u would still have to buy the datalogit for the PFC and a Wideband if you didnt already have one.
Thats my opinion and choice. I plan on running a HX40 in the spring with a Ford Lightning MAF and 740cc injectors and best of all nistune supports it!