Alibab...compare prices..and lease rates buddy..you'll find the 757 is quite a bit cheaper to aquire...running costs are comparible on a seat by seat basis, plus the 757 can carry around 25% more revenue payload further....from a shorter runway
It also has 3 autopilots..compared to 2 in the 800 (I was told that..so Im taking the A/P number in the 800 on face value)