I think that depends what fleet you want to deal with. EC is wanted by many larger fleets, it goes into the leader's pockets. For a smaller fleet they'd like dilithium mostly, but many would like whatever you can give.
We've had people access our t4 stuff before, you can message me in game if you know what you want and will pay for it. @nicha0
EC would help buy security doffs and dilithium is needed for everything.