In an optimum situation, you can earn about 500 miles per hour in Y, or 750 per hour in J.
Segments, each worth the equivalent of about 1050 miles, can be earned at about 2 per hour, or about 2100 miles per hour (again in an optimum situation.)
Now that segments have dropped from 150 to 100 to 95, I suspect segments would be both faster and cheaper in a head to head competition.