Nice job collating the current info!

This is spookily close to my T1 and T2 lists. Just a couple of differences, and the commonality I find most interesting is the number in each tier. There does seem to be a natural break after about 15 pets.

My suggestion is that this list badly needs suggested and preferred breeds, for any newcomer who might use it for guidance.

Yes, it is also very close to my Tier list, which I wrote in the German forum. :)

Breeds are unfortunately not included in the data. Of course I could copy it from my own Tier list, but then it would not be just the data anymore.

And while I know what is likely to be most beneficial, I do not know if that is actually what is most used.

For example, the Zandalari Raptors are probably the best in P/P and S/S, but I also know strategies where you need a P/B one.

That's a great point! I hadn't thought of that. While the site does allow for breed requirements, there are also other constraints like minimum speed or power that are hard or misleading to capture in a list derived from the data.

And indeed breed is not always so simple, and we do keep different breeds for different cases.

I'll drop in the survey answers for the species mentioned in these lists, as a comment, at least. I think it's safe to say that a newcomer will not regret choosing the most popular breed of a species.

Iron Starlette P/P(40%), P/S(23%), H/H(19%)
Zandalari Anklerender S/S(34%), P/P(34%), P/B(18%)
Emerald Proto-Whelp P/P(63%), P/S(23%), P/B(14%)
Unborn Val'kyr H/H(56%), B/B(44%)
Nexus Whelpling P/P(58%), P/S(25%), P/B(18%)
Shimmershell Snail H/P(58%), B/B(31%), H/H(12%)
Nether Faerie Dragon S/S(33%), P/P(27%), H/P(17%)
Kun-Lai Runt P/P(49%), P/S(35%), P/B(16%)
Zandalari Kneebiter S/S(45%), P/P(33%), P/S(18%)
Emperor Crab P/P(64%), H/H(36%)
Scourged Whelpling H/H(67%), P/S(33%)
Mechanical Axebeak P/P(43%), S/S(24%), H/P(14%)
Flayer Youngling S/S(43%), P/P(27%), H/H(5%)
Fel Flame H/P(37%), H/H(37%), H/S(27%)
Cogblade Raptor S/S(60%), S/B(20%), B/B(20%)
Infected Squirrel H/P(68%), P/B(32%)
Twilight Clutch-Sister P/S(53%), P/B(34%), S/B(13%)
Gulp Froglet H/P(43%), H/B(30%), B/B(27%)
Minfernal P/P(28%), H/H(26%), P/S(21%)
Blighthawk P/S(37%), H/P(35%), H/H(21%)
Tiny Twister H/S(44%), H/P(24%), H/H(18%)
Menagerie Custodian H/P(41%), H/H(31%), H/S(28%)
Summit Kid S/S(50%), S/B(50%)
Blighted Squirrel H/P(47%), P/B(32%), P/S(21%)
Sister of Temptation S/B(38%), P/B(35%), H/B(19%)
Jade Owl P/S(63%), P/B(33%), B/B(4%)
Blightbreath H/P(59%), H/S(26%), B/B(15%)
Mud Jumper H/B(63%), B/B(37%)
Lesser Voidcaller H/P(59%), H/S(15%), H/H(15%)
Eternal Strider P/S(75%), S/B(25%)

More about the survey and how to interpret it:
https://eu.forums.blizzard.com/en/wow/t/pet-breed-survey-2019/20349