I know that UPenn is pretty competitive. People who go there tend to want to specialize. I don't really know too much about UPitt though. I am attending Temple right now, and it's pretty relaxed around here, since a lot of us just want to be a general dentist. For all schools, you don't have to be a PA resident at all. Both UPENN and UPitt are private schools, so you pay the same amount of tuition regardless of whether or not you are an in-state resident. For Temple, tuition is about 10K cheaper if you are a PA resident. (It's a semi-public school from what I understand.) We have quite of few out of staters in our school.
Hope this info helps!