High-ranking position vs Relaxed role with a simpler title

I am working for a State Agency notorious for high level of workload by public level standard, but relatively low pay compared to some other Department/agencies.

Now I've been offered/promoted to "Assistant Director" position in the Agency I am currently working with, but at the same time also got offered "Senior Officer" position in another Department. They are on the same level and pay grade (covered by same agreement).

Now, the Senior position will most likely be more cruisy, less demanding and less stressful (unless if I am unlucky enough to get shitty supervisor), but the Assistant Director title will give edge on my CV and provide leadership experience.

Which offer should I take?