I do worry about the likes of Ryanair's policy when an aircraft is heavily delayed. If the next flight is not untilt the next day, or later in the week, and they decide to cancel the flight then you could be in trouble.
My own experiences lead me to think that "non-budget" carriers often care a little bit more about their passengers when flights suffer problems... vouchers, hotels, re-booking flights with other airlines, spare aircraft etc etc.
This is where the difference in your ticket cost can be justified. Not that this is how it should be, though.