Hello, Novice99! I'm just now buying my first artist's grade gouache...so probably NOT the best person to answer; however, be that as it may, I believe in recent years manufacturers have taken gouache more seriously: aiming at lightfastness, color vibrancy, etc. Nope, taint "poster" paint any longer!
Winsor & Newton Designer's Gouache seems to be a favorite with many artists, again; however, Designer's Gouache is just that: made for the illustrator, made to photograph well, not made especially for final, long-lasting art masterpieces. Many manufacturers do have Artist's Grade Gouache: Schmincke, M. Graham, Holbein...among many others. Blick's is favorite reference of mine...you can look up the quality of the paints: Artists, Designers, Student, etc. and look up the pigments each color is comprised of. Another favorite resource is http://www.artiscreation.com/yellow.html
With this, you can look up a pigment number, see what other manufacturers make the color, and also lightfastness, etc.
Hope this helps some...if you do mainly hobby gouache, possibly the Designer's Gouache is the best....if you want longer-lasting results (and possibly better results: less fillers in Artist's Grade) try the Artists!