I've done both and I can tell you that most mothers look forward to going back to work so they can get some rest! I loved being a full time mom because it was so rewarding and fun. One time I had been up all night with my youngest child and fell asleep during the day. Unfortunately he did not and I woke up with his artwork (permanent marker) all over my face, arms, and legs. Fun times! The worst part was trying to decide if I should admit that I fell asleep or say that I just let him do it!
There is a major difference between being paid to perform a service and being rewarded with love for taking care of a child but it's far easier and more rewarding to stay at home and rear a child; yes I said rear! Life ain't easy.
I have always worked full time until I had my little girl. I have been out of work for several weeks now (I have to go back to work) and I didn't realize just how demanding being a mommy is. I think it is definitely more demanding than a full time job but SO much more rewarding.