The top one is a gear start (full crank). The other two are both power torques and look pretty similar to me. The power torques came after the full cranks. The power torque chassis is bigger and heavier also. I prefer the power torque model for this reason but others will like the older model better because it is smaller and lighter - all comes down to your personal preference. They both do an excellent job.
I have both models so if you want any side by side photos for comparison I can post some up.
