MBA vs. MS in Organizational Leadership

[Turkish]

"which degree is the better one to get for someone who is already in a leadership role?"

I think the answer to your question is going to be a little more complex than A vs B.  From my own experience it will depend on the company, positions, school, HR department, etc...
Example - At my work, most of our senior management have MBAs, the schools differ, but they previously decided MBAs were important to get. In the last two years, they've moved away from that with a greater emphasis on focused Masters degrees. That's just my company and not 'the industry' as a whole, but it aligns with the idea that there are a lot of MBAs out there and the market is a bit saturated. However, to directly contradict what I said above, with certain hirings, not having an MBA is problematic depending on the position (if no other Masters is available OR depending on the position itself). Then you come into school reputation. I'm fairly confident with the following fake math.

Harvard MBA > WGU MS Org Leadership.
Harvard MS Org Leadership > WGU MBA.

I understand I've chosen a very extreme comparison, but it highlights a point I think most people can understand.

Lastly, the HR department itself may have biases based on certain schools or degrees (preferred or not) that they may apply. I know there are a few schools we avoid hiring from due to recent issues with recent hires. May just be a few bad students made it through the hiring process, but now the school is perceived to be lower quality due to a small sample size.

Long story short to answer your question, I don't know that it can be 100% answered without knowing a whole bunch more detail, and some of which you wouldn't be able to know.

One thing that I have learned from this board is the price of a degree is nowhere near the value in any sense of the word. Most people are familiar with some schooling being insanely high and not worth the money put into it. However, this board has taught me the other end of the scale can be inverse. Several of the BA/MS level degrees are worth far more than the price. As dfrecore mentions, there's an abundance of knowledge on this board about how to get the most effective return on your dollars when it comes to higher education. With that, I can certainly leave some parting information that may be of use: MBA's at Georgia Southwestern State University, Texas A&M University Kingsville, Southeast Missouri State University, Southern Arkansas University and Texas Tech University are all AACSB accredited, online and cost less than $12K.