Besides the fact that it's basically illegal to own the former?
ES chips come in varying qualities. They can be anything from a very early sample from a stepping that still has bugs, to a late sample that's essentially identical to a retail chip. Sometimes they overclock better than average due to the fact that they're essentially binned, but even that isn't consistent. They're more valuable as collector's items than anything else.
interesting wasn't aware of that. I thought they are mostly samples given out to review sites or PC shops.
Intel Engineering Sample Processors ("Intel ES Processors"), also known as Intel Qualification Sample Processors, are pre-production processors loaned to Intel's Original Equipment Manufacturers (OEMs), Original Device Manufacturers (ODMs), and Independent Software Vendors (ISVs) to be used in the product design cycle prior to product launch.
These processors often include additional features that production processors do not include for customer pre-production evaluation and test purposes. The following conditions apply to Intel ES Processors:
Intel ES Processors are the sole property of Intel
Intel ES Processors are Intel Confidential
Intel ES Processors are provided by Intel under nondisclosure and/or special loan agreement terms with restrictions on the recipient's handling and use
Intel ES Processors are not for sale or re-sale
Intel ES Processors may not have passed commercial regulatory requirements
ES Processors are not covered under Intel warranty and are generally not supported by Intel