Priority & Express mail have a lot more risk envolved. Priority is 2-3 days and Express is 1-2 days, dpends on where you live and where you're shipping to. Then you gotta worry about heat/cold packs lastting for the whole trip and if you ship Priority and it ends of being 3 days and you put a 48hr pack in, you could end up losing everything. Same holds true even with overnight shipping... Some heat/cold packs are duds. Last for a few hours if that. Once you kill a lot of animals shipping Priority and Express you will learn not to use them. They can be effective but not recommended.
As for dry shipping... Thats only for overnight in some cases, depends on the coral. Years ago I was shipped some zoa's (not zoo's, a zoo is place where you keep animals, ZO rhymes with TOE is in reference to an animal...) and mushrooms and ended up with melting zoa's and mush without the shrooms...