E5-2697A is 140 dollars more expensive, not cheaper ( $2891.00 MSRP for A version).
Also, these mathematics need to be done with all-core turbo. But even that doesn't matter anymore if AVX sets underclock : /
E5-2697A (turbo 5/5/5/5/5/5/5/5/5/5/5/6/7/8/10/10 ) so (2.6+0.5)x16= 49.6 Ghz
E5-2697 (5/5/5/5/5/5/5/5/5/5/6/7/8/9/10/11/13/13) so (2.3 +0.5)x18=50.4 Ghz
Also, similarly, they both have same single-core turbo of 3.6Ghz, so there should be no difference if they use it properly. But in cases like this, the one with higher base clock, will always be better for Workstation.
So the difference is marginal and will depend on unpredictable factors. I considered Cinebench R15 to be ultimate measure but the AVX crap thrown this idea away yesterday.
The groups should start after 64, but I will not put my hand into fire for it :- )