in reply to Web Developers vs. Web Designers

I think you're asking a question about a non existant problem :

who has the advantage ?

To my mind it make no sense to say it like that,
Web design and Web coding are 2 NECESSARY aspects.
And super coded but ugly sites won't attract people,
nor superbly designed sites with technically misconceptions
('heavy' pages to load, no interactivity, difficulty to update information...)

You don't wonder which of your 2 legs is more important to walk beccause you need both.
IMHO things are the same in Web site business you need the 2 aspects.

"Only Bad Coders Badly Code In Perl" (OBC2IP)