Nuttz your confusing the Katmai specs with the coppermine designations. There is to date NO coppermine chip with more than (or less than for that matter) 256k cache. The E,EB designations are used to separate the new .18mic chips from the older Katmai .25mic chips. The E and EB chips are identical in layout with the exception that the E uses 100mhz fsb and the EB uses 133mhz.
Both are overclockable, but your success with the EB will be much lower. Example:
600EB (133fsb, 4.5 multiplier) with high quality PC133 (very expensive) and an excellent overclockers motherboard (expensive again) might reach 150 fsb. That yields 675mhz. The system will be flaky and prone to Blue screens, or the worse black screens (i.e. you couldnt even boot far enough to get a blue screen).
600E (100fsb, 6.0 multiplier) with the same setup as above running 150 fsb would yield 900mhz. More importantly though (since most of us cant afford the high dollar hardware) the 600e can be easily overclocked using a decent motherboard and economy PC133 (the cheap stuff) to 133mhz which yields 800mhz.
It should be a clear cut decision which way to go. (600E.. HINT: 600E) Your notion of cache size is correct. Size does matter. Chips with same speed, but one running more cache will out benchmark the other. But when one chip is running 800mhz and the other is only running 600mhz all the cache in the world isnt going to help. (OK, it might, but can you imagine the size of the chip)