What Polenta do you use, instant or corn meal?

I never use instant polenta.

In practice, I'm not fussy...usually use whatever's available when shopping.
Most cornmeals give decent results and I don't find the polenta tastes much different, especially if you are going to be background/absorber of flavors for a highly spiced sauce.
On the other hand, if the polenta is to be served simply with butter and cheese or as a focus of the meal, a high quality stone ground cornmeal will give better results and be worth finding