hi,
i have used both and can tell you from personal experience that usually the doctors prescribe a long acting time release like ms contin 1-2 x's daily and use a short acting med like hydro for break through pain as opposed to the other way around.
ms contin 30 mg three times a day controlled my pain better and more consistently than 10-12 10 mg hydros.
everybody is different. some people just like one more than the other.(or the buzz appeal of one or the other) the narcotic conversion charts are correct chemically. one 30 mg morphine time release is equivalent to more like two hydro 10s, and it lasts 8-10 hours pretty well.
the most important thing though, is that you aren't murdering your liver with all that acetaminophen.(tylenol)
good luck, you might just have to experiment with them yourself until you find the right balance.