I doubt either you nor a middle Georgia Whitetail could tell the difference between any of the round nose or flat point 150 grain loadings from Winchester, Remington, or Hornady. I have no experience with the flex-tip bullets ..... I never saw enough ballistic advantage to justify working up a new load.
If you were to handload, I'd suggest Hornady's 150gr RN over 35.0gr of H335 in a Winchester full length sized case, seated to the cannelure, with a Lee Factory Crimp, and a Winchester Large Rifle primer......