Unless you happened to get a bad one, you'll see soon enough. After about 5-6 tanks of fuel I really started seeing the difference. I ran both side by side on heavy fall leaves for two seasons and have had lots of opportunities to see them try to move the same material pile. When the leaves get deep enough and heavy enough in the pile and the 600 will no longer move them effectively, the 570 (7500) keeps right on moving it. They are both great blowers, but the 7500 is clearly a lot more on real world debris.
Another good test I've put them both to at the same time is blowing heavy sand and gravel from ditches that the snow plows always throw in during winter. They both do great, but again, I can clean crap out with the 570 that the 600 started struggling to do.
The 600 is much better on fuel, but since the 570/7500 holds a lot more fuel in the tank, they will both go just about exactly the same amount of time at WOT. I've tested that over and over again.