I'm here for you!
This *was* my struggle and internal battle for the last year or two but I am in a happy place now! I opted for the part time job, still gives me an outlet for my career talents, gives me a change of scenery so I am not as stir crazy as many of my FT SAHM friends and still gives my kids the 'feel' of me as a SAHM. As DD put it, you are an at home mom, except for the days that you are a dentist.
Some of the benefits of me working are more tangible than others. For us, childcare costs are outrageous, and even more so with the kids only going to a center part time (we don't get a sibling discount or discounts if the kids miss when they are sick or on vacation since we are only part time) so the financial benefits aren't as much as people might think. OTOH, I know my relationship with DH well enough to know that WE need me to WOH, at least some, to keep there from being a power struggle in our relationship. Both of our families had dysfunctional money issues in different ways and we are trying not to have those types of problems. And as far as the kids go, they are happy, they like 'school' and they really like coming to my office where everyone treats them like rock stars!!
What is making you feel like you need a change? Childcare issues, dissatisfaction in the workplace? The more this topic comes up the more I realize that it is so personal, only you hold the answer. When I was really torn about this last year I finally realized that it was a matter of not feeling totally secure in my new office yet and it seemed easier to quit and stay home at the time because I wasn't comfortable yet. As my new workplace has become more comfortable then I realized that I am no longer having thoughts of quitting my job, KWIM? So I'd start by listing the issues and go from there.