Xeons processors are almost similar to Desktop Core 2 Duos and Dual cores, however some Xeons can be compatible with some Intel desktop board since there are some Intel server boards that use the LGA775 socket. This is the main reason why you may have some Xeons as LGA775.
In your case, for the kind of application that you will be running, having greater cache size will be advantageous. From the list of Core 2 Duos and Xeons Dual Core, you can see than the top Core 2 Duos may have better cache, these ones might be better for you. In general, core 2 duos perform better than Dual Cores. That does not mean the Xeons dual cores are not good.
More information about processors can be found on: http://ark.intel.com/
You can compare processors also from this link.
But please bear in mind, before you go for any processors it is advisable to check for compatibility with you motherboard first.
Hope this will be useful.