The HPS, may be good for low key track days, but the HP+ are a good pad too. The HP+ are noisy and create a lot of dust, but they haul you down in a hurry!
I guess it depends on the total time on the track and how agressive your are. It wouldn't hurt any thing to go the HP+
Parking Lot Hero
2008 WRX daily driver
2003 ZX3 23D Autox Car 42 FSP
"Hella Functional - Raced, Not Hard Parked"