USDT (Tether) is IOU and bitUSD is Market Pegged Asset
source: https://tether.to/legal/
more info about bitUSD you will find here:
https://steemit.com/bitshares/@xeroc/what-makes-the-bitusd-than-nubits
Look also for something about HERO ( it's like bitUSD with 5% apr)
https://steemit.com/trending/hero
RE: Safety precautions for the incoming SegWit2x mess