The 633DC would be a little quieter because it is the larger model, but the Vornado will of course also be audible at higher speeds, which is normal, because at a high number of revolutions a correspondingly large amount of air is moved through the room air circulator. With these room air circulators, I generally advise turning them 90 degrees and pointing them at the ceiling, so that the room air circulates without draught, and a lower speed should actually be sufficient. But in general, the 6303DC model would be better, because it is much larger, so it doesn't have to run as fast for a lot of air. Hornbach has a great price for the 633DC, which is available for 99 francs. You can easily do without the remote control and the touch gauges, the 633DC also has 99 levels, but with a very simple control dial.