I would say that Hex would be the preferred move because as you've said you have a Pokemon who can provide an additional status, which increases the power of Hex. Also Gengar can learn Focus Blast which will easily deal with Normal types.
Just read your comment, I would say Hex is definitely the better option as your Breloom has spore which is an additional status move that will double Hex's power.
I'd say go for the Hex.
However if you're not really restricting yourself to those moves I would say Shadow Ball is a better move as you don't have to rely on status at all, and you get a decent chance to lower the target's SDef.