Gengar doubt

Tricky question really.
Lick and Shadow claw are more or less on par with eachother, so just looking at that I would go with the one with best IVs.

However, Psychic isn't a good move for Gengar, so for it to be really useful you have to change it.
BUT....Psychic is a legacy move, so if you care about such things you might not want to change it, which then leaves that Gengar way less useful.
But if you have more with Psychic it might be worth sacrificing it on the one with the best IVs so as to get a better Pokemon.

What charge move does the Shadow claw one have?

Yes, if you intend to use Gengar. (I have a mix of Lick and Hex Gengar, all with Shadow Ball, at level 33+ and they're beasts. I only have Psychic on my 7th, as a novelty.)

Lick Gengar performs better in 60% of the situations he is used in vs SC. I would go with Lick. I have gotten a lot more Shadow Balls off with Lick than SC. And Gengar is about shadow ball.

My disdain for physic on gengar was such that I tm'd the gengar I caught on gengar day right after catching them, if they had good IV.

I find ivs do not make a big difference in already powerful mons like Gengar. Psychic is a terrible move for Gengar. Shadow claw/Shadow ball is the ideal move set. My hex/shadow ball Gengar has bad ivs (%40) but he performs better in pvp than sucker punch+poison attack Gengar with higher iv. So I think base pokemon stats and movesets, and also stab/super effective damage is more important.