Here is a link to a mass CPU round up at Tom's hardware. Including both CPUs. And yes all 2.53's are Northwoods with 512k of cache. Really though the 2.53 is far better value, unless you have no intentions playing games, the 2.53 is a far better CPU. Even if your not playing games a 2.53 would be much quicker in desktop use than a 2GHZ Celeron. Thats why I have one
EDIT: My 2.53 gets to 2.8ghz on the stock Intel HSF before going to sh*t. But the newer C stepping version can get to 3.2ghz+ with air cooling quite easily apparently. By now most of the chips in retail would use the C stepping so if your concerned about getting a B stepping version like mine, dont be. Also a Celeron clocked to 2.66 would still be slower than a 2.53 Northwood, mainly due to the Celeron only having 128kb of cache.