Living in Stuttgart vs. Karlsruhe - difference, experiences...

Hello everyone,

I plan to move to Germany, to Baden-Württemberg, sometimes next year. I would like it to be either to Karlsruhe or to Stuttgart (including immediate surroundings) - so I'm collecting any information on both of the cities.
I would appreciate if someone could give me some experiences on the difference of living in these two cities.
I've been a couple of times in both of the cities (that's how I got to know them), but I never actually lived in any (for more than a month).
I know that Stuttgart is (roughly) double the size of Karlsruhe when it comes to population (cca. 600.000 vs. 300.000), but a smaller size is (often) an advantage (especially in a dense-populated country like Germany).
So, what I am interested in is following:

1) Accommodation - I found some information that rental costs are significantly higher in Stuttgart than in Karlsruhe, but I don't know by what amount. Also - finding apartment - I guess (again) would be more difficult in Stuttgart; but then again I found information that, being a University town, it is also quite difficult to find it in Karlsruhe (especially between semesters - i.e. June-September and January-February);
2) Traffic & Public transportation - which city is more organized? Again, I would say odds are at the side of Karlsruhe (for being a smaller city) and I really loved Karlsruhe's KVV, connecting almost its entire surrounding and reaching even into France. Still - Stuttgart has a U-Bahn. What about navigating with a private car through each of the two?
3) Air pollution - I remember Stuttgart being surrounded by hills, in a sort of a natural "bowl", so I guess smog is there more difficult to escape, comparing with Karlsruhe, which is built on a flat, open terrain - but does it really make any difference?
4) Cultural & other events throughout the year, museums, theaters, etc.

I would thank anyone for any information in advance!