Steam, in the configuration we are discussing (small, mobile power plants) is much less efficient, because water is a poor working fluid which is depleted as it is used to provide power.
Steam turbines, with superheated steam as a working fluid, are efficient in very large plants with access to almost unlimited water for cooling and steam replacement.
Turbines are not engines. Some, are very low and some have got so they are rather high as far as being efficient.
The number of cylinders is absolutely relevant. Lets see a four cylinder ICE produce 6 to 8 thousand HP.
They can not, nor never will.