They all require certain ID verification beyond some balance. Bitmex doesn't, which made it popular by US customers. Also, all of them are terrible for creating a synthetic USD while Bitmex is pretty darn good for that.
Some of the big Chinese synthetic USD exchanges don't require any ID verification.
Clawback is a negative but so is the mex insurance fund, specific users end up paying for it (more in aggregate because the size of the fund has to be massive) through stops.
Anyway who has the best synthetic isnt central to the discussion
2. Funding rate stability. aka it doesn't cost much (or actually make you money) to hold the position.
3. Claw-backs, aka you don't wake up one day and find that half your collateral is gone because the market made a big move. This is a big problem especially for Okex.
Basically, a synthetic USD is good if it behaves and yield like a real USD.
BitMEX isn't going through all this trouble and criminal indictment avoiding KYC because people using it are super on the up-and-up and have no problem with validating their identities.