Alpha 1 has the race base and AR2 core (like in the Pipe Cleaner) which makes it faster, lighter, and stiffer, but a bit more fragile. The Alpha 2 has the S7 base and the AR1 core (like in the AR6/THall) which makes it softer, more durable, but a bit heavier.
The easiest way to think about it is: Alpha 1 = Pipe Cleaner, Alpha 2 = AR6/THall