I've really tried to stay out of this
but hey better than watching politics disquised as sports on the tube. The big problem to start with is the poll doesn't adequately cover some of the better choices. And the "other" category seems to force a choice lumping odd balls and exotics with common calibers like the 375 HH??? No matter
There are simply too many best fits and varying conditions and a wide range of hunter/shooter skills and experience to make much of a sensible recommendation. Anecdotes unfortunately tend to dominate these discussions. Anecdotes work fine for making aware "exceptions" but simply don't work at all for supporting the "rule".
IMO, most PG, with a couple of exceptions, are in the category of small deer to elk size for those with common US experience.
Toughness is however another matter. I think for instance oryx are tougher than someone from the US would associate with common game in the 350 pound range. Both zebra and blue wildebeest seem much tougher than their weights would indicate. Most first time hunters underestimate the size of big eland so add that to their toughness and it makes for some interesting recommendations/discussions for best caliber and bullets. My best advice is to not underestimate the basic toughness of all PG and therefore plan accordingly.
The last time I was there I cull hunted quite a number and variety of PG in an area. I can say with conviction, I did not feel over gunned shooting blue widebeest, zebra and eland with a 375 HH and factory 300 gr TBBCs. A couple of years prior I had hunted trophy eland and shot a particularly large bull with a 416 Rem Mag and 400 gr North Fork CPS and did not feel over gunned. During the cull hunt I shot a load of impala primarily with a 7MM Mag and 175gr factory TBBCs. Even the little impalas didn't just die of fright at the sight of the 7 Mag- an obvious overgunned mismatch for the impala... or so one would think... wrong! Even the inbetweenners like hartebeest, both the larger red and the smaller Lichtenstein's, are no push overs! I gained a lot of respect for them after shooting a Lichtenstein's end to end with a good tough bullet out of a 338-06 and watched him make some distance. The same with a big red who just refused to give up after a near perfect heart-lung shot. During one hunt we even found the bones and head of a waterbuck with horns attached that a hunter had muffed the shot on a few months earlier with a .... wait for it..... 6.5 yadayada. Same hunter lost an eland bull also shot with the 6.5 yadahada that was never found. That hunter had spent a lot of time before his safari telling everyone about his various shooting championships and skills with the 6.5 yadayada.
Considering only rifles I own... If I were going tomorrow for PG where zebra, blue wildebeest and eland were included and had to choose only one caliber/rifle, it would likely be the 416 Rem Mag. If the trip included PG except zebra, blue wildebeest and eland I would take the 338-06. If the species included all up to and including eland and if I could and had the energy for the hassle of taking two rifles, I would take both the 338-06 and the 416 Rem Mag.