Given no replies for days I'll offer a couple of ideas, even tho' i have no experience with your Deda bars. Let's assume the handlebars you ride are identical. But have you measured each?

What is the stem on each bike? Length and angle - same?
What is the stack and reach on each bike? Similar?
Do you have the same saddle-to-bar drop on each?

How you are positioned on the bike will affect the angle of your forearms and the distance your hands must move as you transition hoods to drop. If your Summer bike (more aero?) and Winter bike (more upright?) differ much this may affect what you perceive as a difference in handlebar dimensions.

Other than that, perception always wins the battle over truth.

edit: The bars in your pics do not look the same (to me). Are they from the same year? Maybe something changed? The black bars appear (to me) to have a shorter length on the dropped section of the bar. Other dimensions hard to compare with different camera angles.