AIW Retail includes some cables, an DVI->VGA adapter, and the breakout box (which is absolutely necessary). And a colorful box.
The OEM includes none of the above. I believe you can get them from ATI directly for like $5 ea, $10 for the breakout box. That's probably the $30 difference between the items.
Also, I'm not positive, but the OEM may not include the software!! The ATI software package on the AIW is great, has like 5 CD's of programs, and the defining TVPlus TV Tuner software that gives you TiVo-like capabilities.
Go with the retail. Or search the FS forum, I think I saw one for sale earlier today.