It's completely incorrect to write off AMD processors as 'hotter' than Intel ones, or as 'overclocked' at the factory.
Both Intel and AMD produce many different types of processor - some of these run hotter than others, due to the speed they run at, the manufacturing process, and sheer luck. It also helps to have an appropriate cooling solution strapped to your processor.
Regarding the 'overclocking' of processors - a processor is given a speed rating at the factory (eg, 2.4GHz is a speed rating for an Intel processor, 2400+ is the roughly equivalent speed rating for an AMD processor) and the processor is locked at the factory to run at that speed.
Overclocking literally means running something at a speed faster than which it has been manufactured for, which in the case of processors can only be done in a built system - the speed a processor runs at is controlled by the motherboard it is sitting in (although the processor may limit this speed - factory locking of processors is almost universal).
As a particular processor design has been manufactured for longer, we tend to see the speed of processors produced increase as the company (AMD or Intel) refines and tweaks the manufacturing process. In cases where there isn't the demand for as many high speed processors, we can actually find that the manufacturer will take a processor that can run at say 2.8GHz and lock it at a lower speed and sell it as a 2.4GHz processor. This can, with particular model processors, give the consumer an excellent chance to overclock their processor and obtain a better processor for the same price.
I'd be buying the processor which gives me better value for my money - and this will depend on how much you're willing to spend, and what you're going to do with it.