Dude...
Well first Paul is right about the eMacs, on both counts 🙂 Lets just say, they're 'functional' machines at a good price point, not gonna win Apple any design awards.
Anyhow, if you want some style, along with your performace, you could go either way in the choices you mentioned.
If you have a few extra bucks and enough room on your workspace, i think the Quicksilver and seperate display would make you a very happy camper. You also have EZ access to the insides and are able to expand a number of things, if you so choose to later on.
On the other hand, the iMac is no slouch.... and, pretty nice looking, compact, but def, a bit more 'trendy' than the other setup.
Anyhow... just my 2 cents, good luck with whatever you decide.