The truth is it depends on what you're going to use it for. Multi-core processors for instance are good for applications which require multiple threads of execution, as multiple threads can be executed concurrently. Something like that is going to be useful for web browsing, because lots of different threads are going to be spawned. Compare that to a CPU-bound application like video rendering where a single thread is going to run on a single core in a multi-core environment (where an individual core has a lower processing speed than a single core processor).