I have used ankle weights since starting drysuit diving. They are not noticeable except when i don't have them on and get in the water, when my feet are floaty.
They don't slip about 'cos i tighten them up a little if they are loose.
They are bright yellow to go with my bright red suit
They were a lot cheaper than some of those rip of gator prices i have seen.
They don't tire my legs as far as i can tell, but i tend too mooch around a wreck without lots of finning