Having never duo'd, I can't say much about that. Anytime someone asks me what pets/prey they should use in 1-35, I simply tell them to get parties and pretend to be a war for a while with a tigerfamiliar jug in the usual grind path.
But, to answer, before you have leave, I'd say focus on DC vs EM. The difference in charm duration is massive. DC will often last through two complete mob fights before your pet uncharms, while EM won't. Getting Leave is what unlocks the glory of EM vs T or even VT- in some cases, the ability to reset the charm duration timer before a fight.
Far down the road, when you have AF, you can even consider T vs VT at times, with all the charm+ bonuses on the AF.
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