if delivered power is high , how do you decide if you need to use power combining when choosing the topology?

For example , from imelt /oxide break-down voltage, and from heat and efficiency, and from optimum power matching and output impedance estimation, maybe you can predict how much is a non-power-combing topology will be preferred?  But what kind of metrics, rule of thumb margin and recipe do you usually rely on in determining if you are going to do power combining ?