Buy the seat of the pants, they feel the same power wise.
Matt's tunes have better street manors, they downshift almost immediately when you get on the skinny pedal.
Eric's X-race locks the converter up in 2nd gear, so let's say your cruising around 45mph and start to climb up a hill. With the converter locked, and maintaing the same pedal position with your foot, it lugs the motor down because the converter is locked. The converter wont unlock unless you tap the brakes or lay on skinny pedal. Now you can unlock the converter by either laying on the skinny pedal real hard so it unlocks the converter and downshift, or you can get off skinny pedal, tap the brake and get back on the skinny pedal just a tad harder.
Don't get me wrong, both tunes are great. With Eric's tunes, there is a bit of a learning curve if you want to use it as a daily driver. The X-race is basically a track file, yes you can use it as a daily driver, but it really shines from dead stop to WOT. With Matt's tunes, no learning curve.