I worked 737's and MD-80's when I was working for Alaska and I definatly prefered the 737's.
As far as GSE goes. When I was working with Reeve we had 727's and they sit higher then the 737. We serviced those aircraft without needing beltloaders to get into the compartment. Which was handy since the stations beltloader was out of service half the time.
The 737 does sit a bit higher it isn't so high that you can't jump in from the ground. The rear baggage compartment is a little higher on both aircraft. The pit immediatly aft on the rear baggage compartment does slope rapidly up on the 737 so it does make it a little tricky but on the MD-80 it is flatter but instead of an Aluminum floor it was covered in Gilliner which distorted between the ribs and made it very difficult to slide things on it. The way the doors on the 737 are designed the floor extends all the way to the sill of the door, again it makes it really easy to slide things on it. On the MD-80 the floor stops about four inches or so behind the outer lip. The bottom of the door fits in this space. This means that there is a gap between a beltloader and the floor of the aircraft, Also there are bolt and nut heads that stick up in this area. This again is an area that bags will snag on. Som MD-80's have a fiberglass door that goes behind the outside door. Its purpose is to keep items from falling and blocking the door, This is a good idea 737's don't have it, and anybody who has had to remove a cabin floor to get into the cargo bin will see where this is a good idea. One nice thing about the 737 sitting higher is that the wing is higher of the ground, which keeps it farther away from any GSE that may be operating around the aircraft. Definate safetey advantage. But if you are fueling the aircraft the lower MD-80 wing is better to work with. You don't need a three step latted to get to the fueling/defueling valves. I do prefer the MD-80's three shorter bellies to the 737's longer two.
As far as the ground connects go. If you operate off of a jet way they are better on the left side of the aircraft. If you are using a stairtruck of the left hand internal stairs you really want the GPU on the other side. That way the noise is farther away from the boarding passengers and it keeps the turn around activities limited to one side of the aircraft
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.