Philadelphia Suburbs - Which are best?

[Matt Woods]

I am curious to get people's take on which western suburbs of Philadelphia are best for a buy-and-hold rental strategy.  I am looking mostly at Chester County but am also interested in Delaware County and Montgomery County.  So far I have been looking mostly at Phoenixville, Downingtown, Bridgeport, and West Chester (and a little bit at Conshy/Manayunk/Roxborough). Curious if anybody has significant experience in these markets and can offer any insight? Thanks