I drove 1800 miles in a Hydrogen Car

How does the output and efficiency of a hydrogen fuel cell stack up to a hydrogen burning turbine unit? Are there any limits to just how much pressure and power the fuel cell can make? Batteries have that pesky heat problem and get pretty angry if one asks for an INSANE amount of power for any length of time. 

A Battery powered car would be hard pressed to make 1333 Hp (1 MW) without genius level heat consideration ( at the voltages an electric car would be happy about) - does the fuel cell have the same problem, or can the exhaust water be used as a coolant on its way out? Can the cell even produce 1 MW of energy? 

I have so many questions, I love it!