Dont dismiss the etec because you dont understand the technology. Another thing to check is costs of servicing. Servicing the four strokes is an annual event that can be pretty high cost. The etecs consume some oil which isnt cheap. I paid no servicing costs with my etec for three years. I may have spent a couple of hundred on oil.
Your buying a package, dont get too bogged down on which is the best motor. Weight, servicing costs, fuel efficiency and power calculations are not always clear cut. The biggest will have more torque but it comes at a 50kg penalty.
Try before buying. Go out with the dealers and test the boats with the motors you are considering. You will soon see if any real differences are noticeable. Go out with 3-4 people on board.
Top speed with a 60hp yamaha was around 60km/hr. A 75 should push it to around 70km/hr if propped properly.