Actually, it's closer to an Electra than a 737. You can load 125 laterally on a 737, but only longitudinally on a MD80 (and Electra, among others).
I appreciate the conflict between loader and no. 1 engine on a 737-300 is an issue; we've had 3 nacelle damages in 2 years. But from my point of view that's just about the only advantage the MD80 has over the 737, and I'm not sure that's enough.