I moved it for ya and I'll answer it for ya. How's that for service?
Differences between the Xeon E3110 and Core 2 Duo E8400 is that while the Xeon is a 3GHz Wolfdale core, the E8400 is a 3GHz Wolfdale core. Translation: They are the same. Oh, people will argue this, but sometimes the simple answer is the correct one. One is not faster/slower than the other. There isn't anything one can do that the other can't. One does not overclock better than the other. They are functionally identical, unless someone proves otherwise.
It's like Ford making the Ford Crown Victoria and the Mercury Grand Marquis. Under the slightly different skin and names, the underlying car shares the same factory, chassis, engine, transmission, etc. They are just marketed towards a different clientele.
Now, as to why people are recommending it... for a while the E8400 were expensive and hard to find. The E3110 ended up cheaper and more available, so people were recommending them. Now seems like the supply of the E8400 has caught up with demand, so prices have dropped and they are in stock most places. Whether you buy an E8400 or E3110 depends on which one is cheaper.