I went from an Evo to a Sti. Honestly its just give and take. An Evo has alot of advantages over an Sti, on the Flip side the Sti has some upsides to the Evo as well.
Like many have mentioned its all about what you prefer more. Both are great cars though obviously.
Unless your a "nitpicker" you wont find any drastic difference besides appearance. Both perform great.