Here are advantages to different locomotives (**= compoud locomotive): *4000 class 4-8-8-4 "Big Boy": Length-132' 9" (longest steam locomotive); Power (cyl. hp.)-10,000@70mph (most of any st. loco.), 5,200@20mph. *H-8 class 2-6-6-6: Power (hp.)-7,500@40mph; weight-724,500-778,500 pounds (exact weight unknown; possibly heaviest steam locomotive when tenderless) *800 class/AE class 2-10-10-2**: Tractive Effort (starting)- 176,600 pounds, most of any steam locomotive; only successful st. loco. with more than 16 driving wheels. *AC series 4-8-8-2 "Cab-Forward': best visibility of any steam locomotive; no smoke can get to cab. Z-5 class 2-8-8-4 "Yellow Stone": Most grate area, evaporative heating surface, and super heating surface of any steam locomotive. Add any others that you think are important.