One thing to also keep in mind. If you are flying on two different bookings and a flight is delayed you no longer have a booking with the other airline. I have all to often over the years watched people have big issues when a flight on one airline is delayed and you miss another flight. As a courtesy most airlines will let you standby for a later flight but they are often full.
Make every effort to book all your flights on one passenger record so someone owns your problem.
George