I am deciding on which of these two balls to get. i was thinking about a 920A - but i believe that these other 2 choices will benifit me more in the long run. what i'm looking for is a ball that i will use after my mutant cell starts to burn up and i'm leaving weak 10's. then i figure to switch to the 715T or the 505T. im leaning twords the 715T. any other suggestions, or am i on the right TRACK?