I look at MastSend and there is nothing initially to separate it from the other coins you listed, it just looks like we are late to the party. Something like 'OmniSend' or such that would indicate the cross-blockchain ability would be my preference.
We're talking about names solely for MAST-MAST transactions, so there's no cross-blockchain there.
Ah then my bad. Not sure what I would choose then. PrivateSend and MastSend are both pretty decent.