I do not shoot trap, but am a competitive skeet shooter. My initial thought is that there are considerable variation in speeds between target, game and target, and game loads. This can and does affect your leads on birds. Also, you really should first head to a patterning board to see how your gun patterns with different loads. Most factory shells, particulary the game loads carry heavy paylods of shot, and typically fairly fast. This equates to increased recoil, particularly cumulitive recoil over many rounds and time. Most guys that I shoot with are both skeet and trap competitors and use fairly light loads. 3/4 oz with light charge in handloads. if you like this game, it may be worth it to handload and find a load that patterns well, with reduced recoil.
The bottom line is that there is quite a lot of variation between any factory loads, especially when you go from light target to game loads. If you only shoot factory ammo, I would find a load that works for you, and buy cases of it. Remington Gun Club light target loads are fairly cheap and popular. Good Luck