Tried those type with the prongs on and they keep coming off .i have one fitted to my nuvi 2595 5” screen that is attached with two thick elastic bands and is much better .
I bought the wonderlich one when I had a nav v. They just add a slight shadow over the screen, if the sun is directly behind you your no better off but when your riding into it it’s slightly better. 5 out of 10 I would score it
To be honest I've not used it in sunny weather yet but my experience of trying to see my Nav IV on a K1600 was so bad I'm not expecting the Nav V on my XR to be any better!