Either option isn’t very practical, the hands can’t reach the back legs to slip them on. Therefore I posit that any piece of clothing for a centaur must be put on from the top, like a shirt or a jacket. To cover the legs you’d have to use what basically amounts to a shaped blanket. Perhaps the front legs could have sleeves that you can zip up, but the back legs would have to make do with just the blanket since you can’t reach.