G'day Paul,
How's things?
The name of the diffs (1.5 way, 2 way) discribes the speed that the diff will lock up, and the amount they lock up both forwards and reverse. Reverse being when your de-accelerating (off throttle).
The 1.5 ways are more suited for track work, and 2 ways are for drag and drift. Saying that, they both are better than the stock diffs for drag, drift and track work.
I've got a site bookmarked at home that explains the differeces between the types - I think it's the ATS site. Got good info on it etc.
Try and find someone with a 2 way around your area so you can tack it for a drive and see what it's like.
I found that it's quicker in the corners as the factory diff will spin up the inside wheel very easily while turning, while the 2 way grips heaps better.
If you can put up with additional tyre wear and the noise then go for it. You learn how to drive it on the streets to reduce the noise anyway. For a while there I was thinking of getting rid of mine, but the changed my mind
J