ok i have to play the devils advocate here...
first of all, kirby is as easy to kill as u make him seem... yes he may be light, but he is also small and fast. here we go back to the "pichu effect", making kirby a bit hard to hit. combine that with the best vvertical recovery in the game and proper DI and kirby is a bit hard to kill.
2. kirby is alot faster than u are making him also. i can also play a good fox, so i DO know his speed. grant it fox is a bit faster, but too significantly greater. my guess is u just havent seen a great kirby in action
3. kirby has a world of hurt waiting for fox. any time fox is forced to use his uB (firefox thingy) to recover, its almost a garunteed death, as he is a sitting duck for kirb's dair. not to mention the fact that kirby can combo the crap outa fox. i would say kirb can kill fox just as easily as fox can kill kirb 8)
4. i do agree, in the end it mostly comes down to skill.
NOW LETS GET SOME INTELIGENT CONVERSATION IN HERE!!!