definitely panties over thongs. if you thought walking around with sloppy gusset clinging to your lady parts was a nuisance, try and deal with having to check your skirt/trousers constantly for leaked cum stains!
funnily enough, i find guys seem to like the more everyday underwear than something overly frilly and sexy. not sure why that is. i keep the expensive stuff for special occasions. at all other times it's something quite plain and ordinary with just enough frills to make me feel girly and him feel like he's unwrapping something special.