Vornado733DC Whole Room Energy Smart Air Circulator Fan, Made in USA, Variable Speed Control, White, Large

Q: What is the difference between this and the vornado 660?

Apparently, not much. The 660 has one more speed setting, is a little louder, a little lighter, but more expensive. Source:http://seekyt.com/vornado-660-vs-733-comparing-the-660-and-733/

Q: Would I place this unit near the AC or across the room for best results? If placed near the AC would a more compact model suffice?

I've placed this fan across the room personally and from my experience, the fan does help cool down the entire room as what it does is to circulate the air bringing down the temperature of the room. Because I'm living in Singapore, where the climate is really hot, I usually have the fan faced directly to myself with the AC on and it does get really cold. I've not tried a compact model to further advice but this 733B is definitely a nice addition to my room.