I've done both and both have their upside and downside.  I think staying at home is much harder not just because you are caring for your children, but there are other things to get done as well and if you don't carve some sort of routine out for yourself, stuff doesn't get done.  Working outside the home is more structured and there is an end in sight. While at home you have to make it up as you go along, you never know what the day will bring and the "work" day doesn't end at 5pm.  I think all stay at home moms have the most difficult job in the world.
