Dont know how to answer this let me put my view point
What is SRVCC
SRVCC, Single radio Voice Call Continuity, is a scheme that enables Inter Radio Access Technology, Inter RAT handover as well as a handover from packet data to circuit switched data voice calls.
By using SRVCC operators are able to make the handovers while maintaining existing quality of service, QoS and also ensuring that call continuity meets the critical requirements for emergency calls.
Some ideas for handover require that the handset has two active radios to facilitate handover. This is not ideal because it requires additional circuitry to enable the two radios to be active simultaneously and it also adds considerably to battery drain.
The SRVCC requires only a single active radio in the handset and requires some upgrades to the supporting network infrastructure.
I hope it should clear how it is different from IRAT.
