I've got an OXA on my 618. Really like it.
I looked for one made of steel, not aluminum. I also got a wedge type instead of the piston type. I got a decent deal on a new Shars set on ebay.
It just seemed better in my mind. Other users probably have fine experience with aluminum piston types.
One other thing, get a few extra basic tool holders (i have four). Otherwise, there's little benefit to the "quick change" if you have to remove and replace the cutter every time you switch tasks.