MD80's are built like a freight train. Very solid. Simple, very reliable systems. As a pilot, they are built much better than the Boeings. i.e. thiker sheet metal, more rivits, etc. An MD88 will have modern EFIS avionics, a flight management system and all of the required safety equipment such as Enhanced GPWS, RVSM air data computers/altimeters and TCAS.

Given the choice, I'd pick a flight on an MD88 over one on a 757 because the MD80/DC9 line has only one middle-seat per row instead of two.