PICU months are terrible. I did 2 months. The year behind me got out of the second month. Anybody who claims that they are "running" the PICU as a 2nd year ER resident is smoking crack. Those are some sick kids, and the attending is on the floor a lot. Major decisions are not made by ER residents. The typical PICU kid on my rotation was a single ventrical with transposition of the arteries, with situs inversus, status-post crazy palliative surgery, on three different vasopressors, and lasix, and whatever you thought should be done with the patient, the answer was the opposite.
In retrospect, I thought that PICU was painful, but essential to get a taste of peds. THere are things that you see in a PICU that are in a much higher concentration than you will ever see in the ER. PICUs generally have a ginormous catchment area involving dozens, if not hundreds of hospitals. The reality is that as an ER doctor, you don't admit to the PICU all that often. If you do, it is because pediatricians have told them specifically to go to your hospital to get admitted because they are a transplant patient, or have some crazy cardiac anomaly as above described.
I don't think you should be comfortable going to a residency that doesn't require at least one month of PICU.