I have an Ultra 9, Ultra 7, and Dominus.
One benefit of the Ultra 7 vs Dominus is slight weight reduction. 8oz vs 9.6oz. The other is price is slightly lower.
If you run your scopes as low as possible, you will see the Dominus through the scope more than the Ultra 7.
I don't think the .75" difference in length has any noticeable benefit.
Also, while 2db is measurable with instruments, a person would be hard pressed to differentiate between the two behind the rifle.
Either one is a great choice. I don't think you will go wrong either way.
Not that this is real scientific, but as close to a comparison as I can give you.
.260AI w. Dominus
6.5SLR w. Ultra 7