You will only know the difference if you start with one and switch to another. You are fine regardless which you go with. The 3.73 will lower your 0-60 time and increase rpm at highway cruising speed. Just go with the performance pack. The wheels and diff itself is already worth it.
Not always true, stock car with 3.73 requires a shift into 3rd for 60mph. 3.31 does not and can continue on uo to 75ish.