I have the cast. I really don’t know the difference if there is one. The one thing that may be nice is they now have a point to reduce and auger searching if you have overhead and at the start of the hole. I have seen some pics where people have added the point to an “un-cast” model.
I did have issues with the cast attachment freezing up to the point it was unusable after about 20 holes. SUPPOSEDLY… they eliminated the issue with a different paint on the cast attachment that eliminates the freeze up like many were experiencing. I felt they did a good job in the customer service department exchanging these bits for people but I have yet to test it to see if the problem is solved.
I suspect you are not missing out on much, at least not enough to justify the hundred some odd dollars it would cost to upgrade.