I think that there definitely is huge variation amongst residents with regard to patient volume seen. If you are a patient hog, and tend to leave charting toward the end of your shift, you can see a lot more patients than your fellow residents. If you have an eye on the clock and at 900 pm sharp, you have to go pick your kid up from daycare, you are going to chart as you go and really sandbag it the last couple of hours of shift, so that you can walk out at 855 pm. If you don't have the obligation of going home at 855 pm to fulfill family obligations, you will see patients until the end of your shift if you want to and make sure that no one gets to steal your procedures, just because you are going home. Amongst people with kids in daycare in my residency, the work ethic toward the end of shift was not there, and they were always encouraging everyone to "get out on time!" so they don't look bad running off while everyone else works. Based on numbers in my class that were kept track of by our program director, those with kids in daycare will see 10-30% fewer patients on the average shift.
I would have to agree and disagree with Amory Blaine about having kids making you a better doctor. I personally believe that having kids does give you a leg up on pediatrics. I think the compassion for parenting, and the everyday knowledge of the way kids behave as well as having seen numerous cases of childhood illness up close is valuable knowledge to a physician. My wife won't take our kid to a pediatrician who hasn't had kids (Of course those pediatricians all reproduce like mad anyway). However, overall, I believe that having 2 careers, and a family during residency, without outside help except for daycare, would make you a clock-watcher, would make studying nearly impossible, and would in the end have a negative impact on your knowledge base and overall preparedness.
Another aspect of this debate is that outside rotations are generally utterly ruthless, and don't give a darn about personal problems. Your program has promised them a resident for that month, and you'd better come through with flying colors, or your program director will be all over you like flies on poop. That doesn't change anywhere, anytime. Neurosurgeons, cardiologists, surgeons, etc. don't really care that your kid is sick and it is inconvenient for you to work that day.
People think, "I'll just take 6 months off!" Great, so your residency will be understaffed for 6 months while you are MIA. Then you work 6 months after your fellow residents are graduated and the ED is overstaffed for 6 months because they have to provide you with your extra shifts per month.
I find it a tad ironic that people generally avoid having kids like the plague in med school, and then get baby fever as residents. Medical school is a much better time to have kids than residency, but people don't want their grades to suffer, and keep them from getting into their residency of choice. Once they get into residency, they don't care at all about their education it seems. Once in residency, they will pretty much graduate unless they repeatedly commit malpractice or become a felon or something, so they quit studying and all of the sudden become "devoted to family". As long as their personal lives and goals aren't disturbed, they don't care. If the future lives of their patients might be compromised by a lack-luster effort, they aren't put off too much.
Arguably, 95% of medical school knowledge is pretty much useless on a day to day basis in the ER. The true education comes in residency. These 3-4 years are your chance to learn, practice and ask as many free questions as is possible, and seek as many learning opportunities as is humanly possible.
Again, I will reiterate, that I have nothing against people who have kids during residency, as long as they realize that they really can't have their cake and eat it to. If you have a two career family during residency, for the sake of your training, for the sake of your family, and for the sake of your own sanity, pay for help. Don't expect your program director to baby-sit your kids in their office all day, or think that not showing up at work for personal reasons will be tolerated anywhere. You need a very reliable baby-sitter, family member, or daycare, that is available 24-7, 365 days a year. The alternative is to pawn off work on already over-worked fellow residents. That's not cool.