I'm quite happy with my decision to train at Essendon, dont know much about InterAir but would give NAT a very wide berth. The key to training at Ess is to make your flights of a decent length each time and make any transits between the training area a useful part of the lesson. Pearsons aircraft are some of the most well maintained and looked after of all the training fleets I've seen plus there hire rates are very reasonable.