I'd go with the iMac, though I would (did) go with a pure SSD internal and a significantly larger external.
My current setup at work is a 27" iMac, second monitor (currently an older Cinema Display) with 32g RAM, a 1Tb SSD internal (apps, temp, and occasionally a work file), and some 13Tb total external HD for storage plus another 5Tb external for TimeMachine.