Nubits peg has been broken, not advised to get in on that at this point in time. USDT is similar to having your funds on an exchange, 3rdp party trust.
BitUSD on the BitShares chain is at least backed up by collateral from BTS itself. It is our safest bet at the moment however liquidity can be a problem.
-Read here how it works:
https://bitshares.org/technology/price-stable-cryptocurrencies/-At least create a wallet at bitshares.openledger.info Put in a little play money to see how it works. You can transfer btc along with a list of other options directly from the wallet deposit page, quite nice.
-BACKUP your wallet and brainkey onto an external device. BTS is a web based wallet so if your cache gets cleared, etc... it will lose your keys.
The wallet can be overwhelming with options such as voting etc... so forewarning to be patient and ask questions.