robzzz
Go with the 2.1 Prostock. It can handle hotter mod motors if you wish to go that route sometime in the future. The 2.1 comes with the latest 528 stock. I believe the EX is geared more for pan cars and 1 cell lipo racing. You will need the LCD program card for future upgrades from the Speed Passion site. It makes it alot easier when you interface with your PC or laptop or just alone with speedo.