Actually, there was an abstract at SAEM18 in Indy that looked at this... 4yr and 3 yr programs and compared how many weeks they spend on each rotation. They looked at all 206 (or so) programs and it was interesting that the amount of time spent in the ED was near identical. I'm sure the abstract/poster is on the SAEM website...think it was by folks out of Rush
I found the abstract you're talking about, out of Rush and everything, but it doesn't seem to say what you thought it did:
"Results: 200/202 programs (99%) had data available and the percent agreement was 99.9%.
Among 3-year programs, the mean length of EM home rotations was 76.0 weeks, EM away 8.7 weeks, critical care 16.4 weeks, anesthesia 2.7 weeks, orthopedics 2.5 weeks, trauma/burn 6.8 weeks, ultrasound 2.4 weeks, obstetrics 3.1 weeks, pediatric EM 8.1 weeks, toxicology 1.6 weeks, emergency medical services (EMS) 1.8 weeks, administration 1.3 weeks, elective 6.4 weeks, and research 0.8 weeks.
Among 4-year programs, the mean length of EM home rotations was 92.8 weeks, EM away 13.0 weeks, critical care 18.1 weeks, anesthesia 3.0 weeks, orthopedics 3.0 weeks, trauma/burn 6.7 weeks, ultrasound 2.7 weeks, obstetrics 3.1 weeks, pediatric EM 10.7 weeks, toxicology 2.8 weeks, EMS 2.3 weeks, administration 1.9 weeks, elective 12.2 weeks, and research 1.4 weeks. "
On average, the 4-year programs have 16.8 more weeks of EM home rotations, and 4.3 more weeks of EM away rotations. That's just about five extra months. Not that that tells us the real story: Number of hours in the ED, or at least number of shifts would be needed to make that comparison.
Either way, put me in the camp of 3 > 4 years. If you want to be somewhere specific for a geographic reason, fine, but it's not like residency is your last chance to live somewhere. You could always move out there as an attending as soon as you graduate from your 3 year program. There does not seem to be a widespread decrease in shift burden (shifts per month) at 4 year programs as compared to 3 year programs, to answer your question, OP.