Don't bother posting on the green site. They can't even get the classes right trying to compare a 9770 to an 8120. This comparison - 9570 vs 5088 - is a case of an actual class 5 ( the 9570) compared to a fake class 5 (5088 - actually a de-tuned 2388). There is no way on God's brown or green earth a 9570 will come close to performing equally to a 2388. The 9570 is a smaller rotor diameter, and smaller in all other cleaning/separating stats. Much less a small engine cranked to the max.
This is a no brainer, the 5088 is the superior machine, stats - wise. After that, it will depend on dealer, cost, your love of green or not. Remember, the 5088,6088 and 7088 are basically a 2388 with different horsepower/engines and grain size to match the classification requirements and priced accordingly. You cannot increase horsepower on the 9570 and get 9670 production because it is physically a smaller machine. A true class difference on the green side.
If you are really serious about this comparison, go to the Deere and CIH websites and compare the specs.