The learnability is the fundamental difference between an phonetic alphabet and a pictographic one.

Renowned educator John Taylor Gatto has a pretty interesting analysis of this in his book "The Underground History of American Education". Rather than belaboring his points, I'm just going to link to it (by the way, the rest of the book is also online there, and is a good read if you like this sort of thing).

http://www.johntaylorgatto.com/chapters/3k.htm
http://www.johntaylorgatto.com/chapters/3n.htm
http://www.johntaylorgatto.com/chapters/3o.htm
http://www.johntaylorgatto.com/chapters/3p.htm

(edit: added more links to relevant pages. Recommend the whole chapter, or at least pages 10 to the end)