How many of you are there? If it's more then just you then I say rent a car or hire a service. Price wise alone it will be real close.

A car will be in the $60 to $70 range for a day's rental with the drop off at Philadelphia. The drive is about 120 miles between the two airports, and you will be after one rush hour and before the evening one.

Drive it,, either yourself or hired. If you drive, map it out in advance, and follow the advice to stay out of Manhattan.