My personal opinion is, that both are good - in their own right(s). Both are different from one another.
Anyway, I'd suggest playing <img src="/ubbthreads/images/graemlins/div.gif" alt="" /> first, because thden you might understand <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" /> better, and why it was formerly called <img src="/ubbthreads/images/graemlins/riftrunner.gif" alt="" /> .
Another thing would be to look out for the novella by Rhianna Pratchett - to me it's like "background information" of <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" /> and the "Riftrunnery". <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
There was once such a "background story" for <img src="/ubbthreads/images/graemlins/div.gif" alt="" /> as well, but I don't know where you can access it via the web. Has anybody a link to it ?