pool is better than line. you can't milk a line ride by going the long way. you can't stop new requests or cancel added passengers.
whereas with pool, there are places and times that i specifically look out for pool rides because i know that i can make more money with a pool ride than with an x ride because i know the tolerance for how long i can stretch a pool ride without raising the fare charged to the rider.
i won't take pools in the city or hood, i will take pools in the suburbs, i will take "long trip" pools.