While I've heard Deribit has a good customer support policy, its user base is far behind BitMEX because it offers a limited menu of derivatives to trade and a lower max margin.
Meanwhile, SimpleFX just hit 200k users because it is able to outdo BitMEX's leverage while being able to offer even more trading pairs. Hence, it stands a much stronger shot at disrupting BitMEX's dominant market share.
Thanks @hatu! Will definitely check out SimpleFX. Great that BitMEX is getting some competition. Are you familiar with Digitex Futures exchange?
I have heard of it; it has hype but the platform hasn't launched yet. It'll definitely be interesting to see how it performs in terms of functionality and UI.
Though, when it does launch, its leverage won't exceed 100x, as has been stated by the founders.
Am also very interested to see what the platform looks like. They are scheduled to launch April 30th. Have been keeping an eye on $DGTX since $0.03 and saw it hit $0.09 the few days ago and busy retracing now, so will keep an eye to see how far it dips down. Didn't buy in, because I don't like HitBTC or Mercatox, but would like to see how they preform over the next couple of years.
For now, it's purely speculation. Can't say how Digitex will turn out.