During my residency, we had peds cardiac attendings who trained at BCH and CHOP. I know a few residents who went into peds cardiac at each institution. They all said great things about their own institution and they mostly stayed there as an attending after. I think it comes down to your preference for location. Of note, one of my coresidents at CHOP told me awhile ago that they are either building a new institution or expanding. Not sure how it will affect your training time at CHOP though. Both excellent places to train.