Wallet Style Preferences?
I would have assumed that bifold wallets are the most popular for men. But this Kiplinger's article says trifold wallets are still the most popular. It quoted one 1996 survey that showed trifolds are three times as popular as bifolds for men under 20.
The main advantage of a bifold wallet over a trifold is that they're thinner since they spread out the contents over a wider area. Also, there's one less fold. A thin wallet not only makes it less visible in pants but also reduces the stress on the stitching and other parts of the wallet that may crack. So the bifold wallet should last longer.
According to the article, the main reason why trifolds still are the most popular is due to habit. Men get trifold wallets when they're young and stick with this style as they age.