The original Dying Earth RPG has much more flavour, which is missing from the Revivification Folio, both in terms of reading and rules. The Revivification Folio has cleaned up the conflict rules, so those are worth yoinking. But I'd personally keep the rules for different refreshes for different things from the original, and magic as well.
One thing about the RF though - the scenarios included are absolutely excellent, and way better than the one included in the original book.
I've only run The Dying Earth once - I want to do it again.
You have to have a feel for the Dying Earth and Vance's style in particular. We always found that the players would help to come up with stuff on their own. Which reminds me I have a scenario half done about the long distance delivery of a 7' tall wedding cake to finish...it helps if you have sense of the ridiculous