Fiber is always recommended for MAN type links. Know that protocol analyzers look inside packets to trouble shoot problem. Know that connectionless is quicker but less reliable. Connection-oriented is slower but more reliable. Gateways - protocol conversion.
Routers cure broadcast storm.
Bridges make it worse. Its all in how they handle the broadcast. Know that T-1 lines operate at 1.544 Mbps. Know that PPP supports data compression and dynamic addressing and supports multiple protocols.