Apple doesn't skimp out on parts. If they're using two manufacturers, they are both good manufacturers. The polka dot problem aside, they are both obviously good screens, as seen in this post.
I have a 7 series and have tried as hard as I possibly can to find those dots, and I can't. My brightness can be outrageous, to the point that at almost all times its down to about 10%, and my colors are gorgeous. Anytime I see photos of the two together, the 5 series ends up looking washed out, so I'm very happy with my screen. People shouldn't worry so much and just be happy they have a well built, very nice phone, no matter the parts!
A part in an Apple product, no matter the part, is still an Apple product.