Let's think about this. If stage 3 is better than stage 2, but they're the same price, would anybody ever buy stage 2? And if nobody ever bought it, why would they even offer it?
The reason they have different cams is because they have different uses. I don't know the specific specs on the cams, but typically a "stage 3" cam builds power in the higher RPM range, but it at the sacrifice of low-end power. This is great for certain racers that are constantly screaming their engines, but not so great for trail riders and racing that requires a lot of low-end performance and throttle response.
You need to analyze your riding style and find out where you want your power to be, and build your engine (including camshaft choice) around those needs.
Duncan Racing 340PV, +2 A-arms, +4 LSR axle, and a host of other goodies.