From my (2weeks) printing experience with the Ender6, I noticed that the amount of infill plays a big part in the overall speed of a print. The maximum increase in overal print time is achieved while printing solid parts. The Ender6 takes 50% less time than my Ender3 with a 100% infill part. With 20% infill its about 30% quicker than the Ender3.
Since most printers, like the ender 3, print at 50/60mm/s what Creality really means is: it moves 3 times as fast. Not: it finishes a print 3 times as fast.
Still, i think they've done a great job with the coreXY system. For me printing 2 times as fast really floats my boat!