We use the Incident module for both Break/Fix and for Requests. This is the was HEAT was originally designed - there's a field called "TypeOfIncident" that can be unhidden, populated with a pick list to denote Incident or Service Request and put back on your Incident Details Form. Then your SDA's just choose the type as the ticket is assigned but they can still search for everything in the one module.
We use both Service Request and Incident. Out-of-box there are searches for My Items which covers any type of ticket.
We used to do it the other way but this has been working very well. Anything a client wants/needs is a Service Request and anything broken or a password reset is an Incident