I suspect the Pentium D 945 would be better but there are no real direct benchmark comparisons between the two.
But by taking the 3DMark06 CPU test results from:http://www.xbitlabs.com/articles/cpu/print/core2duo-shootout.htmlhttp://www.hardwaresecrets.com/article/577/8
Celeron E1400: 1646
Pentium D 945: 1743
About the same with the 945 just ahead. I'd expect the Celeron to overclock quite nicely, easilly scoring higher and running cooler so I'd go with that.