Univac was faster than IBM’s machines.

IBM was better at marketing.

IBM’s computer systems could be retrofitted to work with the old punched card technology. This met less equipment had to be purchased, and there was less worker re-training. The downside was that the full potential of their computers could not be used since these slow access mechanisms were always in place.

Univac did not use punched cards, they used magnetic tape, a far technology superior that was faster to read, write, and could be re-written. (Re-writing? What a concept!)