Math vs Math Education I have a big decision to make in my life right now, and there seem to be three likely paths I can take. 
(1) PhD in Mathematics Education 
(2) PhD in Mathematics, with an Education Option 
(3) PhD in Mathematics, and just taking graduate education courses as time allows. 

For those who are not familiar with things like (2) describes, here are a few examples:
http://www.mathed.soe.vt.edu/Programs/MathPHD_Educationoption.html
https://www.cmich.edu/colleges/cst/math/Pages/Program-Requirements-for-Ph.D.-in-Mathematical-Sciences.aspx (II.2)
https://wmich.edu/math/academics/doctorate

I'm very much interested in both math and math education. Specifically, in math I really enjoy problems in graph theory and discrete/computational geometry. I'm finishing a master's in math this semester. 
In math education, while I have completed only two graduate courses, I am completely fascinated by writing cognitively-demanding tasks, interviewing students to observe mathematical problem solving strategies and thought processes, thinking about ways of assessing mathematical understanding, and most recently preservice elementary teacher education. 

But which of the three options above would be best? In the long run, I would like to be employable in a mathematics department, with the freedom to do research in math education. Further, I really need a program that is funded and includes a moderate stipend. While many math PhD programs include this financial support package, I have not seen many math education PhD programs that offer similar packages. 

Please share your thoughts. Thank you in advance.
As far as I know, university mathematics departments with any kind of significant research focus do not hire people who have a math ed. degree.  You need a math degree if that's where you want to work.   Even the education option will only hurt your chances of getting a tenure track job in a research-oriented math department. 

If you do some searching, you'll find that people with math ed phds are generally employed in education departments rather than math departments.