I tend to look at the Cult bonuses this way, myself;
Strife - best overall for mech Wyches
Cursed Blade - best overall for foot Wyches/Wych blobs
Grief - best overall Succubus (optimal Patrol purchase)
So it really depends on the goals of your Cult. With what you have here you're kind of walking the line between Strife and Grief to my mind, because you're buying the bigger detatchment with them, and also because you're kind of taking some tie-up Wyches and also a killing squad.
I would suggest that since your core strategy appears to be a killing
HQ assault tool, probably Red Grief does remain the best choice, as your other tie up tools will be overall better. But, yeah, you could go to the whippy Strife Succubus at only a small shift down in the
HQ effectiveness and the speed of your tie up units to gain extra overall Wych impact.
Personally i'd advocate Red Grief because I like the option to headbutt Landraiders to death with my Succubus - but I am perhaps in a minority there