Both the RM7710 and Garmin 9165 have some glare issues. Both are the same sort of 7" screens with very shiny surfaces, not a matte finish. They will wash out in bright sunlight, just like most laptops and other screens with similar technology.
The RM does have some optional (extra cost) add-ons to reduce glare; a snap-on hood and a non-glare screen cover (their words). Haven't tried either one yet.