by all means, check local libraries and colleges for OED access - if you have a library card, you may have online access to the OED via proxy server! The Minneapolis Public Library offers this service. of course, there are obvious advantages to having the CD-ROM, but the online service offers the latest data base and has fixed a couple of noxious little problems the CD version has.

as to the MW v. AHD debate, I would still opt for MW, and I wonder if they've updated in the last couple of years, perhaps adding audio (the online version now offers this, keeping up with AHD/Bartleby).