Well, it all depends on what you're looking to do in the future and how much stuff you'll have on the site. A lot of people use 3 column (including myself) because I have a lot of info on my site... and you don't want people scrolling down forever...
Im not sure regarding better for adsense but im going to be working on a 3 colum blog and probably a few more 3 column afterwards too, for some reason i think they allow for a little more.
The 3-column template is more popular than a 2 column template . But if your stuff fits well in a 2 -column template then it will be fine too .
I prefer the 3-column template, I can put my adsense code in one column and have space for the other blog thing in the second column.
General column question to you all, do you guys, when having 3 columns go for a left column, main content, right column, or do you sometimes go for the main content to one side with both columns side by side? Do you think the latter is pushing the main content over too far to one side?
In my opinion, a 3-column blog (sidebar on the right) is the best possible layout, in terms of monetization possibilities and the overall look/feel. There is a lot more space "above the fold" for ads or for other content you would want to promote on your blog. So, if you want to maximize the money potential of a blog, I'd say go for a wide, 3 columns theme. Otherwise, even 1 column is good
You should always use 3 columns blog when you have a lot of information and make it available and easy to access to your users.