bacsidoan wrote:May I remind you all that under the same tension, it takes less force to create the same deflection distance on a longer string.
But what matters here is whether you are plucking at the same distance from one end or not (if it is the same, then the angle of displacement would be the same, so same effort to displace). If you are plucking at about the same distance from the bridge on the 660 vs. 650 guitar, you would mostly feel the increased tension on the 660 as the contribution to the restoring force from the string displacement would be about the same or small compared to the increase in string tension from the scale increase.
I suppose if I am right, then fretting at fret 1 would feel more difficult (rather than less) on a 660 than on a 650 as fretting is a displacement, and the distance from the nut is about the same, so you would mostly feel the increased tension from the scale increase.
To throw in another possible factor: The feel
of tension when pushing (displacing) the string could also be one of more effort when the string is thinner (for the same tension) - as it digs more into the finger?