Also depends how fast you swing... if you like to take big, powerful swings its better to use a smaller racquet. But if your more of a steady type player, the bigger frame will give a little extra power without you needing to swing faster.
Big Head means more power but less control, and vice versa for a smaller head. Look on thewomens side at the Williams sisters who had massive racquets using the Wimbledon N4 and N3, really way too big for professionals or even decent younger players. I have not seen any male player use an oversized racquet