I see both sides of a SAHM and a working Mom.
I am also a RN and work per diem, usually nights and weekends. So, while I consider myself a SAHM, I also work.
That being said, both are difficult. I do have to say, for me, working is easier. I work on a med-surg floor and float to a telemetry floor which is pretty easy. I also work per diem for hospice. Although nursing may be stressful, I think I have more downtime, more adult interaction, more breaks and more "me time" at work than at home.
Again, this is me, and my opinion only. I'm not labeling anyone else. So, I guess this is my UO.