IMO it is easier to work on a bigger tank. On a small tank if your levels start to get outta wack you have to "Be on top of it" fast. But with a larger tank the levels will not skyrocket "as fast" I have a 180 gallon an once it is up and running, i only have to do a water change. I dont even clean my glass, snails do that for me.
I would say go with the 75 if you have it already.
If you don't, i actually have a 72 bow that i am looking to get rid of.
Have the tank, wooden stand, Wet Dry filter, UV steralizer, BASIC light strip. So basically all you would need to get my setup runnint right is a new set of lights and a skimmmer. PM me if you are intersted.