Just to put it down nicely before someone else does it meanly.
The core is really a rip off.
First off, to even SAVE a game you will need to buy a mem card ($39), so that means you are only 60$ away from getting the premium.
Now, you also:
DONT get the wireless control ($49 to buy it separate)
DONT get HD Cables ($29-39 separate)
DONT get HDD (No Demo Downloads, Not much space for saves, $100 Separate (Just the HDD makes up for the price difference between the Core and Premium!)
DONT get headset (no talking on live)
So if you buy a core, NEVER buy a HDD (hard drive) as that would make up the price difference between the premium and you should have bought the premium then as you get the HDD and a bunch of other stuff....
If you can, just wait till you can afford the premium, its only a 60$ difference when you add in that you NEED to buy a memory card with the core cause no one can live without saving games.