I have 1 Grand Prix ii (had 3 but just gave 2 to my gf) and it's a large standard (Fench?) chefs knife. It does seem to me that the Shun is sharper, but judging sharpness isn't really an exact science.
I did also sharpen my cheap Chicago Cutlery knives to 15 degress. I think i have a few that are old 440 steel and a few new ones with cheap 420 steel. I know they wont hold the sharp edge. In fact no matter what I do it seems I cant make them feel as sharp as the good knives. I bought a sharpener that was supposed to let me go down to 11 degress but the silly thing hits it's own bracket except on the smallest blades.
So, my conclusion is you just cant make a really cheap knive good even right after sharpening, but a good knife can be very good; and there's more too a knife feeling sharp than the sharpening angle or honing. I may work more on trying to get my Grand Prix ii to feel as sharp as the Shun but at this point I may just live with what i've got.
BTW i also got my gf a Shun Primer and I really like it, more than the classic. Although I'm not really sure why. My gf is like oh, you got me a knife? Why? I hope she'll use her bad knives then swap to the good knife and then appreciate it more. I had given her a custom made tool steel from Wildfire cutlery, but she got it discolored on the first use so i realized non-stainless just isn't going to be for her. Now I'm hoping she doesn't use the Shun for a prying tool.