I never really gave the column view a chance. To me it seems a good layout if I only look at a few mails and provides enough detail to not click on them. Classic compresses more data into the same space and you see the adress and subject grouped together which I think just gives better overview if there is a lot of different stuff.
I would argue contrary to another poster in column view you need more folders to keep mails of a different sort better separated to maximize on the strengths of the mini previews. Otherwise it is just a waste of space.
I have the col view in the notification bar but in the Mail app I prefer classic as I think it is better at handling a lot of mails at one time. The notification bar is for the 1-5 mails which in col view save me the time to check them out individually.