This is the 1 MUSD question when you start a new product development.
First, both can be used when designing a high power/ high voltage application, say 3 kV/10 MVA.
Second, if you are used with IGBT technology, it is tricky to enhance your scope to IGCTs- there is a lot to develop around them.
in most of the applications the IGCT is more compact and reliable than its counterpart, but you need to be experienced with its mechanics and protection.
Consider that the IGCTs are produced mainly by ABB and used by ABB and Siemens.