Jason's response is dead on.

I ran the older PD models for many years. I upgraded to the Terrova last year and Love it. I like the foot pedal on the Terrova much better than the older PD models. I have AP and co-pilot..

Maybe it's just me, but it seems that the "auto-pilot" on the terrova is much smoother and provides much better control than the other PD models.. I have ran all of the PD models at one time or another and the Terrova is best in my opinion.

Can't wait for I-pilot to get here.

Find a couple of fishermen close to you that have the two different models on their boats.. Ask them to take you fishing (offer to buy gas or something) and test drive the two units. This might help you decide..

Good Luck