You are thinking that boxes give better items that packs, but it's because you buy more boxes than packs. But i think it's really random, because i didn't always get a legendary one in the pack, and if the pack gives 5 items, when i would still have a good chance of getting a legendary one if i bought 5 boxes. But i never tried it, because i think that buying 1 box, i have 1 chance to get what i want for just 1 attempt, while with the pack, i have 5 chances for 1 attempt.