I also have the neu 5000 hardpack and really like it. I run it in my T4 for the indoor season. Also as you said the price is very good on them. I dont think there is any difference in performance compared to my flightpower 4900 car pack but it will save you about $20.
If the Neu 5000's were around when I bought my Trakpowers, I'd have bought them instead. However, I'm pretty darn happy with my Trakpowers. I did pick up a 3S Neu 5000 a while back though. It's going to be my speed run pack for my VXL Rustler and Stampede. It may also find its way into a T4 this weekend to try some speed runs with an Orion Vortex 5.5.