Gitzo tripod, which one?

I'm in the process of purchasing a new tripod and my Manfrotto 055xPROB just isn't steady enough since I got bigger and heavier lenses. I was looking at both Gitzo 3531 and 3541 but I would like to hear some more advantages other than price and closed length comparing 3 and 4 sections legs. Common sense tells me that 3 sections should be sturdier than 4 comparing the diameter of the fourth section but the 3541 seems to be the most popular on this site.

Also, for those that don't have the center column, was there ever a time you wished you had it or is it a complete waste of money?

Happy Holidays

Marc