We are purchasing our first CC bay boat. In the past we ran deep v walkthrough windshield (mountains of Colorado). What are the advantages and disadvantages of mounting fish finder flush or gimbal?

I have 2 Lowrance Elite 9 Ti's mounted on my console. Set up side by side I run one for mapping and the other for graphing. When searching an area I can side scan with both having one look left and the other right. I thought of mounting one in the console just never got around to it after over 3 years. Only down side to mounting in dash is if you ever upgrade then you either have to go larger or hope it has the same cut out. That or have the dash reglassed or covered in starboard.

IMO many more advantages to gimbal mount than flush mount.

1. Security
2. Weather
3. Adjust for sun position and distance to eyes.
4. Reduced trailering shock

Ditto on what others said above.

The unit is in the weather 24/7 unless the CC is stored indoors. There will be times you don't use it for many weeks, so why subject it to the elements 24/7?
If the unit fails, you have the hole to deal with.
If you want something different, you have the hole to deal with. Even if you are getting a larger unit, will there be room to fit it there?
If you go to the boat one day and the hole is empty, you have a stolen unit loss to deal with. (They'll probably just cut all the cables too, and that's expensive to replace as well.)
Being able to adjust the angle is a very nice feature as discussed previously.