Yeah, I’ve yet to find an FX broker that offers agreeable conditions for cryptocurrency trading, that would be suitable for my trading style. Regarding the 15% taker fee – that is actually only the case when using maximum leverage, fortunately. Personally, I think that the taker fees are still too much. I can generally get away with using limit orders when exiting a trade while trading crypto on the exchange, but I usually prefer market orders, especially when entering a trade.
But, any relatively decent crypto exchange that offers leverage has shied away from the idea of entertaining US traders, for some of the same reasons that FX brokers do, so there is the added risk of exposure that comes with trading on those exchanges. That, and, as you say, the leverage for crypto trading via an exchange has yet to really get interesting, in my opinion, especially for more exotic or volatile pairs.
Personally, I would rather trade cryptocurrency, if I could, but I have gravitated towards FX because the conditions currently seem more favorable for traders. Perhaps that may change someday, but it may be a long time before the liquidity is comparable.