i stayed at the same place for undergrad and med school and i am very glad that i did. there were many factors that went into the decision to stay in salt lake.
as far as personal reasons go, it has been nice to have my family somewhat close by. it has been a lifesaver to have so many non-med school friends around. that factor, in and of itself, makes my decision worth it. there is something to be said for knowing your way around the city. the skiing and biking are unparalled here. i could go on and on.
it was a fairly easy decision for me to make. tuition here is ridiculously cheap ($15K), which is key because i am racking up some serious debt right now at a private law school. if i had gone to a a private med school i would not have been able to enough think about going to law school. it has been great in other ways as well. because i know the administration so well, it has made getting problems solved that much easier.
i certainly understand the desire and need for a new location (hence my decision to move back east for med school), but the decision about med school was easy.