I think the main thing people like about Nubits above all else are the buy and sell walls which give them the confidence to go in or out. They are able to suspend looking too deeply at the risk that this depends on sellers not outnumbering buyers for a prolonged period. If that happened the buy walls would fall (as they will represent an increasingly small fraction of the growing supply), and unless shareholders were willing at that point to prop it up by committing the profits they have received (and potentially spent) along the way from their NBT sales, the peg would break and owners would be left with something of much lower value. While demand increases uninterrupted, the game can go on, potentially a long time. When the flaw is ultimately exposed to the masses however, there will be no coming back.
It doesn't matter to people right now, but the big difference with BitUSD is that it is (over-) collateralised (albeit by BTSX which is volatile), and its supply can shrink automatically with lower demand. If BitUSD could also create buy/sell walls, it could compete as well as hold a higher ground.