there is a lot you can do with a larger tank. Just because you have a 150 gal tank doesnt mean you have to break the bank turning it into a reef. Why not go fowlr? Save the reef for the smaller systems. You are going to spen money either way, nobody gets into this hobby because it is cheap. With a reef you are going to spend money on lights, controllers, reactors, chillers, additives, and corals. With fish your are gonig to spend money on uv sterilizers, life guard filters, etc. i do not have fowlr system but that is going to be my next purchase. Infact I am looking in the sunday paper to see what I can get. But I already know what I dont spend in lights and etc, I am going to spend to keep the fish healthy.
As far as system up keep goes, ya it is bigger water changes. But the little fluctuations that can be detrimental to a smaller system will have less of an impact on a larger one. More water volume to dilute the little flaws, so to speak.
I say go big, your going to do it eventually anyways. Do it while you can or else your always gonig to wonder what if. If you get in over your head, you can sell it off to someone else in about a weeks time.