I switch between dcs and fsx a lot, one thing that keeps me coming back is the ability to fly a combat aircraft "with fangs" around areas I recognize. Sometimes I park the bug on the deck of the Nimitz, set full steam ahead toward the middle of the Pacific and not come back to my computer for a few hours. Then launch off the deck in the middle of the night in the middle of nowhere knowing that I have nowhere else to land other then back on the deck of the carrier. Obviously FSX has a lot of work arounds and sometimes feels artificial while DCS is much more streamlined for combat but it would be hard to replicate something like that in DCS at present.