I went into the store with my B30 to compare: B30 was HEAVIER than the B35! Both are Togo leather, even the SA was surprised. Are they using a thinner leather? It felt thinner and of a lesser quality...plus it was slouchy already...my B30 is only 18months old so I'm surprised the obvious difference between the bags.
I preferred the black B35 PHW for everyday heavy use as it looks more casual, I like the slouchy look. The raisin B30 GHW is more stiff and more dressy, I tend to use my Chanel collection for evenings so I have literally used the B30 3/4 times in the evenings and never during the day.
Oh what a dilemma to have? I know a lucky dilemma but dilemma all the same.
Sounds like you have made your decision

Your chanel bags are better for evening than the 30cm (which is a tote and not a dressy bag) and since you haven't carried it during the day, perhaps you should just sell it.
You will make somebody else very happy and you can get the bag that is more useful for your lifestyle.