I need some help with my wheel set up and cassette choice. I need to replace the cassette on my training wheels I have been thinking about making a cassette change. Here is what I use:

WHEELS
Race - Mavic Cosmic Carbone (currently using 12-25)
Training - Bontrager Race Lite (need cassette)

CHAINRING
Ultegra 53/39

Most of my rides are flat, but I do some shorter hill training during the winter months. I have been using a 12-25 on both sets of wheels but don't use most of the inside or outside gears.

I have a new 11-23 and was thinking about putting it on my race wheels and using the 12-25 for training.

My races on mostly flat with some short rolling hills, nothing requiring much climbing.

What do you think the benefits and weakness of this possible set-up?

Thanks in advance.