HJC 2010 gives you precise control of your curve radius and rotation rate about the bar. Most approach calculators make you choose what stride you will start your curve on. This gives you only two or three choices of curve radius which, in turn, gives you only two or three choices of rotation rate about the bar. That's not good enough. To clear the bar efficiently, you must control the rotation rate about the bar exactly, which means that you must control your curve radius exactly. HJC 2010 gives you that control.
HJC 2010 preserves your run length regardless of what other approach parameters you change. You don't need to fish for your starting point each time you adjust your approach.