The "S" is 16.5' vs. 17', with the same hull design. So I doubt there would be that much difference in tracking. I have tried other kayaks where only the lenght changed and the tracking was barely noticable for even a one foot difference. In severe conditions you will notice it more. But for fair weather kayaking, she will probably like the shorter and lighter "S". And the 1" wider will mean more stable, which will be more noticable for someone used to canoing.

Just my opinion. I am planning on builting a "S" for a girl friend, when I am done with my Guillemot. She need more stability. :-)

Gordon