#10 is approximately 12 tons; #9 is about 18 tons. #9 is larger overall than #10, which you'd expect for another 50% of engine.
#10 also has a very small boiler and firebox, which greatly affects how much steam it can generate while working. It's a good engine for either small trains (1 or 2 cars is ideal) or short distances (a mile or two), which is why Edaville (which liked 5 or 6 car trains for its 5 mile loop) didn't use it once it returned from Pleasure Island.
#9 is much beefier than #10 as well. The frame is thicker, parts are bigger. The boiler & firebox is also much larger, allowing for greater steaming capacity.
#9 is what I like to call a long distance engine. It's designed to operate a long ways between needing water and fuel, which is exactly what you found on the SR&RL, KC, and WW&F. #10 was designed for operating around the flat sugar cane fields and factory, where it was never far from water or fuel.
