Incident and Change Management in two separate SW tools?

Answer:
Generally, I would suggest to keep all processes in one tool i.e. that you manage all processes with single SW solution. Reason for that is that you will have all information in one place and many information will be transferred automatically between process activities (e.g. you enter only once information in Incident Management and them when you open a Problem ticket or Change request - same data will be transferred). If you don't have that (you asked for risks) - then there is a chance that some information will be lost (e.g. asset information which you need for Incident management as well as Change Management).