Steam Turbines vs. Gas Turbines

I see that you have had no responses to your question. This is not because there is no one out there who knows the subject, it is because your question is far too broad and would require a huge amount of effort to answer, even in general terms.

In very general terms, gas turbine has lower installed cost/kW and higher maintenance cost, less reliable and more frequent maintenance interval and lower efficiency.

The maintenance activities on the two machines is just too different to discuss in general terms. One has a compressor, combustion system with extreme temperatures, the other sees clean steam.