1. One who is present in the synagogue at the same time as the congregation are praying, may not pray earlier than the congregation as it appears as if he is degrading the congregation. If he is in a hurry because he must leave on a journey (some add that even if he is in a hurry because he must go to learn Torah), he should go home and pray there. (Shulchan Aruch and Mishne Berurah 90)
2. If, however, the congregation are procrastinating by saying Piyutim or other extras, and because of this they are not going to reach the Amidah before the final time for praying, he should hurry and pray even in front of the congregation, so that he should not miss the time for praying. (ibid)
