I've done casting tests on the Form1 castable resin and it didn't cast as well as I'd hoped. Still leaves bad surfaces and some porosity. I haven't been able to test the material from the B9 (though not for lack of trying), so I cannot comment on how it casts, but I've heard good things. From what I've heard, you'd probably have an easier time casting the material from the B9, but you'll have an easier time getting consistent prints from the Form1. Plus, I believe the B9 resin is considerably cheaper than the resin from Form1.