85mm 1.8 vs 18-200mm 3.5-5.6

 I rented an 85mm 1.8 lens from LensRentals.com.  I wanted to see if this would be a better a lens for taking pictures of my son playing basketball.  The lens I currently have (18mm-200mm 3.5-5.6) works fine for capturing the game but I would love to have a lower fstop to capture more light.

The 85 was a little slower than my current lens but I loved the DOF and how much light it captured. It just created a better over all picture quality. However it was a little too much zoom for where I normally sit in the stands. It was hard to capture the player and the ball when they were shooting 3's .

I guess it depends on what kind of photos you are looking for. My son likes the pictures pulled back a little bit so he can see more of the "game" in the pictures. With the 85mm we both felt the pictures were more about the individual player than the game itself.

So....not sure what to do. I would definitely want this lens for the end of the year tournament where my seat is further back and for portraits.  Should I go ahead and buy it and practice getting the kind of shots I want? I took this lens on a family get away and had a hard time because I could not get back far enough half the time to get everyone in the picture.

Taken in the same gym, same lighting but on two different nights

85mm 1.8

18-200mm 3.5-5.6