What is the best USDA rated beef best for stew in a pressure cooker?
So, understand that MANY recipes were developed to make poor choices of food products chew and taste much better.

Stew is one of these that allows a tougher cut of meat and some older veg stored in the root cellar to be made tender and tasty.

However, all other things being equal, no matter why a recipe was developed, using the highest quality of meats and veg will always produce a superior product.

So the best beef meat to get for a stew would be prime grade beef, and fresh veg is the best to use for the best flavors and textures.

One more however though. There are diminishing returns on goodness versus price. You don't need prime beef for stew. It will be amazing, but is it worth spending $40 for the beef rather than $20? That's up to you and whether you want to 5 star your stew that was really designed to make halfway inedible stuff decent to eat.