Okay folks - I give in! What the heck is a vortex - I guess it's nothing to do with fluid dynamics. Then I spy this, "I'm still 50/50 Vortex vs. SnS". My brain 'hurts!!!
it's a metal cone, like the ones dogs wear when you need them to stop licking their nuts or chewing their tail off - except it's metal.
it's useful for making a single very hot spot, or for making a ring of hot and indirect heat. There are claims to other methods of use, but after multiple attempts I am convinced that the other usage methods are a waste of time.
The SNS is the Slow'n Sear. There's no comparing. Vortex is a one trick pony that is easily replicated.
SNS is an accessory that lives in the grill and improves the function of the grill, even in multiple cooking arrangements and methods.