Dual Core VS Dual Processor

Which one is better?(ignoring costs)
I'm thinking of making a dual core system, but woundering if one is better then the other, and how so.

Multi-processor systems are better for both single and multi-threaded, Single threaded apps can run on a single CPU that will have access directly to its own set of memory, seperated from background processes. Multi-threaded apps get more memory bandwidth due to each CPU having it's own RAM, whereas a single dual-core CPU still has to force threads to take turns waiting to access the memory bank. Cache misses are not as significant when you can have 2 threads simultaneously execute, and simultaneously access their own memory spaces.