Speed altitude (fly over weather). And also reliability (less maintenance)--Know-fear
CORRECT!
Even though back then jet engines were notoriously fuel inefficient compared to prop planes (and still are), the maintenance costs over the lifetime of the aircraft were so much lower that it was the driving factor. MTBCF also played a role.
Sorry for taking so long to reply...i am still restricted to one post a day.
Now back to NWBO...the above analogy also applies.