Peppermint used to come in two flavours: One, built upon the Firefox browser; and Ice, built upon the Chromium browser. Jolicloud 1 was built upon Firefox. Now Peppermints One and Ice have become a single entity, Peppermint Two, built upon Chromium; and Jolicloud is now at version 1.2 and also built upon Chromium. For the last few weeks I've been alternating both OSs on the same i386 256 RAM laptop (a cheap Proline machine bought by the company I work for).
What I've noticed so far is that Peppermint is amazingly fast on this limited hardware, attractive to look at and to use, and very open in its design. By contrast, Jolicloud is sluggish, obviously requiring more RAM than this laptop can deliver. Jolicloud's design is also compromised by the bigger-than-netbook screen and gives the feeling of being a more closed approach than Peppermint. This makes sense really, since Jolicloud is trying to give bigger devices a similar look and feel to mobiles.
I think therefore that Peppermint Two will remain on my laptop while Jolicloud relocates to my netbook, for which it is no doubt better suited... although I have a sneaking suspicion that Peppermint Two will do better there as well.