When was it said that they would be 8-C+ to High 8-C?
But anyways...
Attack: At first Abraxos downscaling from a baseline High 8-C, so it should be close to that tier. Keywords: "At first".
Durability: Abraxos, see attack.
Lifting Strength: Azurill, Superhuman > Abraxos Athletic Human.
Stamina: Abraxos, Extremely High > Azurills regular High.
Range: Azurill, hits at max 10 meters with its tail compared to Abraxos several meters (2-9 meters).
Intelligence: Supposedly Abraxos, as Azurill is naive, but that doesnt mean Azurill cant fight.
Experience: Equal? Abraxos age is unknown and Azurills can vary.
Abilities: Azurill. Remember the time I said "At first" earlier? Well this is where it gets played. Tail Whip is pretty beneficial to lower Abraxos defense, down to 25% of Abraxos original attack from stacking it 6 times (the max). Azurill is also able to lower Abraxos Attack via Charming it. By the time the debuffs are applied, Azurill now takes the AP and durability. While I see that Abraxos can fly, special moves should be beneficial, especially Bubble Beam, which can lower its speed (but its a 10% chance of landing the slow effect). Abraxos can hide, but it cant delay its fate once the effects are applied. Assuming this is Huge Power Azurill, that makes it a HUGE advantage once the wyvern is weakened. And if its on the ground, Slam does high damage, and adding up to Abraxos debuffed from the Tail Whip, this WILL do extra damage and it will most likely be defeated within a few good hits.
Conclusion: Azurill pretty much takes this via Bubble Beam to slow the wyvern down first, then debuffs it to make it weaker. Abraxos as far as I can see does not have any projectiles, so it has to get close to attack but then it will be Charmed, Tail Whipped, Bubble Beamed, or even another good attack that will take down this wyvern.
Thus, I will vote Azurill.