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Both Intel® Xeon® Processors are Tray; this means the processors are pre-installed on Server systems (OEM). They are from the same family.
The E5-2699V3 has more cache memory: 45MB. It has 18 Cores and 36 Threads and requires 145W.
The comparison chart provides with the main features of the processors.
The processors are compatible with several boards; however, it is necessary to contact the system manufacturers and request the list of models available with these processors.