NPC....
Lets first make sure we are talking about the same thing.
By "overhung" I assume that you mean -horizontal axis, end suction design ( e.g. ANSI process pumps)
By "between bearing" I assume that you mean what is commonly called "double suction" in the pump industry.
There are many advantages/disadvantages to each type.
Suggest you purchase/review a text such as the "Pump Handbook" by Karassik.
-MJC
I suggest