Never used any of these stable-coins. When I need stable coin, I use USD.
I'm trying to stay away from USDT. After reading a lot about it, I can't trust them and I'm really sceptical about it.
Never heard about Havven? Which exchanges have it? I would like to see more information about, because I tried tosearch and didn't found anything.
The most stable-coin is USD. If you consider the so called "stable", why do you think about investing crypto coins? You should keep your USD.