Here is my opinion as a Peds EM fellow who did peds first and is now doing a PEM fellowship - for whatever the hell that is worth...
If you did Peds first as a residency, than PEM is a pretty competative fellowship to land. There were approximately 200 PGY4 PEM spots out there this year, and the application rate was about 2.5:1 (2.5 applicants for every one spot), which is high, since most peds subspecialties do not fill since they do not get paid for crap, and are mostly required to work in academics, which does not pay well.
Doing a PEM fellowship for a pediatrician is a good step up, ... if you like the ED. The upside is shift work, a pretty good life style without call, not having to deal with general peds office crap - ADHD, behaviour probs, developmental disability (hey, if you like that stuff, than power to you!) and better money (in both academics and private world - these are very rough, off the top of my head #s)
Academic General Peds start ~ 110-120K, max 160-170K (not administrative or department chair, etc...)
Private Gen Peds - depends on the practice set up and regional location
start ~130-140K, max 200-250K if partner
vesus
Academic PEM start ~ 140 - 150K, max 180-220K
Private PEM start ~ 200-225K, max ??? (rates vary with variable benefit packages from $100/h -$170/hr, average probably 125-135/hr)
Again, the money is not as good as your adult ED comrades will make(but who the hell likes sick old people? j/k), but it can be significantly better than gen peds with a better lifestyle.
As an adult ED person... I do not really get the draw. If you really like kids or if you want more experience, or if you want to work in academics doing both adult and peds EM, then, OK. But otherwise, why would you want to train more with deferred compensation for two years, then do time in a Peds ED where you will get paid less? Again, if this is your bag, come on down, but I do not see it.
Again, just my humble, FOS opinion.
Peace,
Greg