Before virtualization concept/technology, each node such as MME, SGW etc were combination of specific hardware and software. There is a technical term vendor locking. Vendor locking means if an operator wants to deploy a particular node such as MME, it has to buy a box (hardware + software) together. For vendors it was a profitable business model but for operator it was more CAPEX/OPEX. Now using virtualization technique, all these nodes have been decoupled from hardware.
Now these nodes run in the form of virtual machine also known as VNF (virtual network function) and these VNF/VM are instantiated in data centers (public or private clouds).
In order to reduce CAPEX/OPEX, operator would prefer to deploy vEPC components and at the same time many more players will jump into telecom node development because of removal of hardware dependencies.
This is my view of seeing vEPC v/s normal EPC.