Apart from the price, the Rolleiflex usually came with better faster lenses, although you'd need to research various models as there were so many lens variations. The Rolleicord had a knob winder and I think the shutter cocking was a separate action, whereas the Rolleiflex had a crank wind which advanced the film and cocked the shutter in one operation. There were other differences like the Rolleiflex probaby having a brighter focusing screen.
Of the the two models, the Rolleiflex was considered the 'pro' camera, but many a pro earneds his living with a Rolleicord.