I have not zetad talzin. So can’t speak for that. I have double zeta asajj. Personally I really love it. It’s invaluable in raids. Really great in arena. Climbed under 100 in arena first time with ventress lead.
Speaking just from theory... I would say talzin lead would probably be better vs zaul leads while ventress better vs. chirrut/Baze teams. Talzin would be slightly better vs cls lead (debatable) for more potency on stuns for focus fire to avoid counters.
I would say ventress is probably better for more variety of things (raid, arena, DS TB). But purely arena I would say talzin is probably better. She has fewer weaknesses from what I’ve seen.