That's a good point -- depending on where you live and work EWR may not be that much less convenient than PHL. From most of Bucks County, EWR is not that much further than PHL. From northeastern Montgomery County, as TWA Fan 1 observes, it's a wash. From most anywhere in the city or the Western suburbs, you're much better off with PHL.

I'm not sure I'd agree that getting to EWR is necessarily a huge challenge -- from Center City or University City or the Eastern Main Line it's easy enough to get to 30th Street Station and thence to EWR -- but it will certainly take more time.