It's subjective, and situational. So I'll just give my choices with some justification.
Also note that some pets are still very scarce, so there may still be undiscovered breeds (Pierre, Rascal-Bot, Kovok, Blackfuse Bombling, Moon-Moon, Dandelion Frolicker).
For the moths, I would choose P/S. For Ashwing and Skywisp, there's some reason to choose H/S instead (to keep the flying passive up longer for Alpha Strike/Counterspell). I'd be happy with either.
Azure Crane Chick -- you have to take either Surge or Reckless Strike, so you really don't want speed. I don't know what I'd do with this guy, but I'd choose PP or HP if I used it.
Blackfuse Bombling -- PP is awesome, HH is awesome -- if there's an HP it will be good too. Hard to go wrong here as long as you don't invest in speed.
Ashleaf Spriteling -- assuming you go Poisoned Branch/Wild Magic/Thorns, you want to make the opponent hit you as many times as possible before you die. With no heals, health is the way to do that, but he maxes out at 1400 health with the BB, which is pretty bad. The alternative is to make Thorns etc hurt as much as possible, which you'd do with the PP or maybe the PB. Power would also support Roots if you went with that in slot 3.
Ruby Droplet -- scales best with the opponent's health, which you can't control. Assuming Absorb/Bubble/Drain Blood, health is your best friend, with power only contributing to Absorb. I chose HH, but HS (to make Bubble into a better avoidance move) or HP (to make Absorb better) are not bad choices.
Dandelion Frolicker -- you want to annoy the opponent to death with Kick and Frolick, so you want speed. And because your plan is to stall while hitting often for small amounts, the humanoid passive is very valuable. So health is also your friend. SS gives you the best chance to be faster, which is the most important thing -- but if you think you can be faster with 289 speed, then HS is actually very good.
Death Adder Hatchling -- this is a really great pet, and another case where you'd want to gamble with speed: you want to be faster for Blinding Poison, but you don't want to overshoot the opponent's speed by too much or you're giving away stats elsewhere. The SS has 341 speed which is pretty massive; PS has 305 which is still pretty good; and PP has 276. You gain a lot of damage potential when you downgrade the speed, so he's very situational. The 'safe' choice is SS, but PS will be much better against any team without a 300+ speed pet. Personally I grabbed all 3, but I bought/leveled SS first.
Droplet of Y'Shaarj -- for the AoE setup, you probably want PP. I grabbed a PS because it was available: it's ok, but I'd rather have PP. Sandstormers are the biggest reason to want speed, and they're slower than the PP anyway. I'm kind of disappointed in this guy in any case -- Acid Rain+Dreadful Breath is not that much damage by 5.4 standards.
Gooey Sha-ling -- not impressed with this guy in general. Presumably he's supposed to be a healer-buster, but he's got no burst to go with Call Darkness/Breath of Sorrow. Both of those abilities last multiple turns so going first isn't a big deal for stopping heals, and anyway he bottoms out at 260 speed with the PP. I'd go PP if I ever played him.
Jademist Dancer -- potentially a ton of damage. Some people like SS but I chose PS, because Geyser goes off at end of turn regardless of speed, and when he manages to do Geyser/Rain Dance/Steam Vent/Steam Vent, the opponent is stunned on turn 4 anyway (or swapping). Because of the crit rolls, the damage this does will vary wildly, but on average it's 1800 with the PS, and 1680 with the SS. Since SS is 'only' 317 speed, the various 325 pets will still outspeed you. So the question is whether you want to go faster than 289/305 pets. In return you get a lot more leeway on your combo -- the PS will kill a 1400 pet with 0 crits whereas the SS won't; the PS will kill a 1681 health pet with 1 crit whereas the SS needs 2; etc.
Kovok -- so far there's HH, HS, HP. He really really wants power for Pheromones, so at this point I'd choose the HP. If a PP shows up it might be a tough choice, because he has surprisingly little base health. HP is certainly very good though.
Skunky Alemental -- his abilities lend themselves to trapping a pet and brawling, so you want him to be hearty and be able to dish it out. None of his abilities particularly benefit from speed, and there's no PP, so I chose HP. HH wouldn't be a bad choice either.
Spineclaw Crab -- this one is tricky. It's tempting to max out power for Blood in the Water. However he is relatively fragile as a PP, with 1319 health. You can overcome this in part by taking Healing Wave, in which case you absolutely want PP. The problem with this moveset is that after you Rip/Blood in the Water/Healing Wave, you are stuck Ripping for mediocre damage for 2 turns, or swapping out. The alternative is Rip/Spiny Carapace/Blood in the Water, but the problem with Spiny Carapace is that it's only good if you can get hit a bunch of times. So you'd really like some health for this moveset, ie HP.
Gulp Froglet -- kind of a discombobulated moveset. Frog Kiss is the only ability asking for speed, and he tops out at 276 so Leopard Tree Frog is better anyway. Between BB, HP, and HB; HP is the clear winner, but I don't see myself using this guy in any breed.
Bonkers -- this is an interesting case, similar to Flayer Youngling. Obviously, you really really want to go first. So SS is the safe choice. But you gain an awful lot by having additional power, and with humanoid passive you also gain a lot from health. So there are good reasons to gamble with speed. And if you know the opponent's speed, ie in PvE, then you can choose optimally. For example PS Bonkers still goes first versus Yu'lon, and the extra 29 power over the SS makes a big difference against her shield. Considering the annoying way this guy is obtained, I would never throw away a SS, PS, or HS.
Gu'chi Swarmling -- speed seems like a waste when you can only get to 289, his best matchups are versus UD who tend to be slow, and Chew/Acidic Goo are end-of-turn anyway.
Rascal-Bot -- so far there's 2 breeds on petsear.ch, PB and SB. I would lean toward SB for Lens Flare, since 276/289 are pretty common speeds. Armageddon wants power, but the difference between 289 and 273 is too marginal to concede going first against a decent range of pets.