Currently - bench marking between the two algorithms, c29 & c31 seem to have roughly equal rewards. Marginally, c31 is ahead.
Hardware used: 1080ti's & Vega64's, both running on Minerbabe.
Not sure how that works out... I get 3.4 for c29 (GrinPro on Windows), and .43 for c31 (kbminer/minerbabe on Ubuntu) on a Vega64 @ ~165W. Plug those into the calculator you have posted you'll see that rewards for c31 are double c29.
Edit: more like +70% currently, after this recent c31 spike.