Unquestionably ----- the CHESAPEAKE.
Probably 'most' Philadelphia and S. Jersey area sailors with larger boats (<30ft) prefer the (Upper) Chesapeake ..... about 1-2 hours drive from the Philly area. Most favor the Upper Eastern Shore (rural, unspoiled, uncrowded, 'mannered'): Sassafrass R., Worton Creek, Fairlee Creek, Tolchester, Rock Hall with Rock Hall probably having the most amenities, boat services and best proximity to Annapolis, St. Michaels, Baltimore and the 'mid-bay'.
The Delaware Bay has essentially ZERO marinas, few 'ports', is very buggy, is very shallow and can have very strong tidal flow - not much 'boating' on the Delaware Bay with the exception of Cape May, NJ. If you like 'pristine' low-country wetland wilderness and being 'totally on your own' the Delaware Bay may have some appeal.
The Delaware River can have strong/swift tidal flow, is the 'drainage' for mostly city/suburban areas - not very 'scenic/bucolic'.
I live ON the Delaware R. between the 'mountains' and Philthydelphia.
My recommendation for anyone in SE PA & S. NJ is the Chesapeake.