There is no single YES or NO choice between 754 NC and CH, otherwise such question would not keep coming up, ....
The final choice is up to individual call, and depends on a few factors. Assuming in the context of cost-effective system:
There is no clear evidence, beyond the underlying randomness, from the sketchy results, that NC can be overclocked 150 MHz higher than CH consistently, to overcome the bigger L2 of CH, from the result collection.
A64 Overclocking Result Collection (2nd post)
NC is easier to get, whereas CG CH w/ 1 MB L2 is harder to find, except for mobile/mobile DTR CH.
The NC 3000+ is $30-50 cheaper than a 3200+ CG CH w/ 1 MB L2. They both have the x10 CPU multiplier which is considered more flexible in setting up a system than a 2800+ NC (with x9) in terms of HTT and memory bus. x9 is still doable for overclocking, if saving money is a high priority.
Further, if one wants to go with NC 3000+ (w/ 512 KB L2), then I think a 90 nm 939 Winchester 3200+ which also has 512 KB L2 is a better choice for its new revision, higher memory bandwidth (for memory intensive applications), future 939 upgrade flexibility, ....
IMO, this is my preference:
1. 90 nm 939 Winchester 3200+ w/ 512 KB L2
2. 130 nm 754 ClawHammer 3200+ w/ 1 MB L2
3. 130 nm 754 NewCastle 3000+ w/ 512 KB L2 ($30-50 cheaper for CPU)
Performance analysis of various A64 systems (including Barton, P4's) (post 7)