Best and quickest way is to take a look at the IGE charts for both models. Pick a OAT and run the line down to the altitude where you can hover at max. weight. Anything higher will need a weight reduction due to reduced power available of the normally aspirated engine. Now look at the chart for the turbo model, pick the same OAT line and see how much higher you are able to go at max. weight. This shows the increased performance due to the turbo's ability to hold rated power to a high density altitude.