23mm v 25mm rim width

mickisup Posts: 295
edited August 2014 in Road buying advice
Can anyone give advice on the merits of either? Looking specifically at Cyclocross wheels and options are 23 and 25mm rim width.

Bearing in mind tyres will be 32 or 34mm I am just wondering why there is an option of 23 or 25 for the rim itself.

Many thanks