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The relative difference in light gathering power purely by the numbers for 120 over 100 is 1.44 and 132 over 120 is 1.21. (Squared ratio). There will be a difference but the jump is not as large.
Resolution difference will be perhaps less pronounced than light gathering to the eye but noticeable under ideal conditions. Contrast can affect the perception if there is a considerable difference in f ratio between the two.
I base my comments on many observing sessions with both Astrophysics 6” f12 Super Planetary vs 7” f9. The 7” f9 gave a clearly brighter view of Mars but the contrast between light and dark features through the 6” f12 was clearly more remarkable. Syrtis Major was quite dark in the Super Planetary! I only ever used these telescopes for the planets when I was fortunate to have time alone with them. I did use both at the same time on occasion just to compare. The relative difference light gathering between these two is 1.36.
As much as I liked the 6”/f12 for contrast I welcomed the brighter view at similar magnification (difference eyepiece to get this) in the 7”/f9. Eyepieces used were Nagler Type 1, 2, and Clave Plossl/Clave Barlow. It was all a long time ago now.
Personally I think it would be worth the jump but other factors such as cost, weight and size and mount requirements come into play. A jump to 140mm would be nicer at more cost, weight and size.
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