+Crit rating, dodge rating vs. +AgilityFollow

Does anybody know how the math works out on gear with +Critical Strike /+Dodge rating versus gear with + Agility. I am thinking about crafting Stormshroud Pants: http://wow.allakhazam.com/db/item.html?source=live;witem=15057
but before investing 20-30 gold in materials, how would they affect my stats versus a green item with agi/stam, for instance Wicked Leather Pants:
http://wow.allakhazam.com/db/item.html?source=live;witem=15087

If the effect is fractions of a percentage on crit% and dodge%, it doesn't seem worth the gold.