What is your objective with your connections? For example, NYC-DFW-LAX is about 150 miles more than a non-stop NYC-LAX. If you're after the miles connecting in MIA will give about 1,000 miles more than the non-stop, connecting in SJU will give 2,500 more. If you're not after miles why bother changing at DFW? Same for SFO-NYC.