>>52558537Palafin.
Adult-level Digimon are usually strong enough that you'd need an above-average fully evolved Pokémon to take them. But Palafin is definitely above average, and Dolphmon isn't anything special as Adults go. Only risk is that it manages to evolve to Perfect mid-battle.
Aqua Dolphin has weak stats and is used mostly for its support effect (which at best would translate to Disable or PP sapping) or fusing with Neos.