Definitely a much smaller difference in economy. However, most people (it seems from the discussions here and from a few personal discussions I've had with RTW travelers) buy F or J, partly for the comfort in so much flying and partly for the added miles and/or status credits. Recent changes to the booking class of economy RTWs and (if one is in the AA program) to the mileage credit for discount economy fares on partner airlines has made economy RTWs relatively even less desirable than before in this regard.