My recent impression was that ÖBB is hidden from new arrivals, and that CAT is presented first and most obviously. As a first-time visitor, I passed a lot of green CAT signs before finally discovering the ÖBB window. Having watched your previous videos about what to do, I was determined to not use CAT! ÖBB is less expensive, and has more frequent departures. Just be sure to buy a proper ticket before you step on the train!
You can buy it directly from the ÖBB vending machine. € 3,90 already includes a one way ticket within Vienna. Highly recommend checking out our full airport video on RU-vid to make sure you buy the right tickets.