I'm using both for German (in between taking formal classes). They each have their strengths and weeknesses.
Pimsleur (as well as Michel Thomas) do a far better job of teaching you to speak the language functionally and understand what's being said. You certainly command the grammar when speaking much better than with RS
. I absolutely love doing these two systems.
, on the other hand, does a much poorer job of teaching the grammar (at least in level 1 and the first half of level 2, which is as far as I've gotten). You do learn far more vocabulary, but it seems very disjointed, since (especially in the beginning), all of this vocabulary has no context, other then some very simple sentences (ie: they'll teach you the words for "boy and girl", then simply force you to continually repeat these words, eventually giving simple verbs like "run".) It becomes very nausiating after a while, since all you're learning are words, but never actually using them functionally. I really wouldn't recommend this for you, since you likely have a good command of the language, so will find RS
incredibly tedious and boring.
While I've never used it, I've heard very good things about Assimil With Ease self-study course books. They do indeed have a Chinese system available, and they claim that their course will leave you with 2000-3000 words. I would say to look into this before going out and trying RS
Hope this helps!