There are pros and cons....steel headgaskets actualy have probably more issues than composite ones and guarantee nowt.
Composite ones suffer due to poor coolant maintenance and in the case of a design floor in an engine (i.e. K series), are prone to failure if there is much movement.
The steel ones can leak for what appears to be no good reason with often water ending up in the oil (they suffer less with water to combustion chamber issues). The composites tend to rot (due to poor maintenance) which means the fire rings are not fully supported and hence you get coolant to combustion chamber issues or very occasionaly water leaks.
Two examples.
K series Rover - has some nasty design issues which means that the composite ones get a hammering, in theory the steel ones would help...a bit!
Rover V8 - Standard steel ones suffer all sorts of failures.....the later engines had a composite one fitted which sorted most faults out!
So, horses for courses.....fitting a steel gasket could in theory also increase your compresson ratio....(they are thinner) but, I favour the composite ones and good servicing!