The
E5-2651 v2 is based on
Ivy Bridge architecture while the
E5-2670 v3 is based on
Haswell.
Using the multithread performance as a reference, the E5-2651 v2 gets a score of
426.2 k points while the E5-2670 v3 gets
338.7 k points.
Summarizing, the
E5-2651 v2 is
1.3 times faster than the
E5-2670 v3. To get a proper comparison between both models, take a look to the data shown below.