Right now I am on Concerta, 54mg. I have tried higher dosages, but the drowsiness and inattentiveness came back. This is what originally lead me to believe that the effects (stimulant or depressant) of substances are relative to the person's dopamine reception. At a higher dose of Concerta, 72mg, I figured I'd end up being superhuman, but, surprisingly I ended up back where I started - inattentive and unmotivated. At Concerta 54mg, I've noticed marijuana will often push me over this threshold as well, causing the marijuana to act as a depressant where it was otherwise a stimulant.
Ritalin, while chemically similar, doesn't seem to provide the same benefits from those who've disclosed their experience (again, anecdotal). Concerta is once-a-day release-controlled dosage.
My experiences very closely match yours, fwiw. I tried Ritalin but wasn't satisfied at all, and am 'back on' weed.