If legroom is a consideration, UA offers Economy Plus, which has a few inches more legroom for a reasonable fee. Also, you can check seatguru.com when you are ready to book your flights to see what the seats are like on the aircraft you'll be flying. I am partial to the international terminal at SFO. On the day of travel, if you find you have a lot of time between flights, you can purchase a one-time entrance into an airline lounge to get a more comfortable waiting experience including snacks and beverages.