Differences between HD and full HD gaming

SO iv'e been thinking about buying a new xbox360 elite. My family recently bought a 48inch full hd sony bravia TV, however i only own one of the original 20gb non hdmi xbox 360's. So i've been wondering for a while now whether it is worth buying an elite because i need a bigger hard drive and want to have full hd games. With the announcement of the new 360 prices for elites have dropped to about 250 bucks here in Australia.

So anyway my main question is: how much better do games look when playing on a full HD tv with a hdmi chord?

Is it worth buying the Elite for this?

PS i don't want to buy the new slim 360 because i will never use 250gb of hardrive space (i've only just filled up my 20gb after 4 years) and i don't have wi-fi so some of its major capabilities are useless for me.)

I noticed that when playing a game in 1080P (full HD) its alot more detailed, you can see the texture on your soldiers shirt from his arm on Call of Duty: World at War. The image is alot more crisp. I feel like the colors also might be a little enhanced but idk. I figure you should go for it, I mean you want a bigger hard drive and you even have a full HD tv. Take advantage of it! :D