The oneworld alliance have two round-the-world tickets: Oneworld Explorer (OWE) and Global Explorer (GE). Basic difference is that OWE is continent-based (world is split into 6 - N and S America, Europe, Africa, Asia and SW Pacific) and the fare varies depending on how many continents you visit and class of service (econ, biz, first), while GE is distance based, and fare varies depending on distance travelled (split into three bands) and class of service.

For maximising miles, OWE has a lot of advantages (there is a four flight per continent limit, apart from N America which allows 6) but with a cap on total flights at 20. Therefore you can fit in some DFW-ANC, PER-SYD, LHR-DXB flights to maximise miles. However, GE does allow you to use codeshares on non-OW airlines which can be very useful if you're trying to get to/from PPT, for instance.

More info on OWE available here, and there's a ton of information in this forum (probably literally, if you printed all the threads out ).

Enjoy !

Stewie