In 2019, I personally like Bitfinex and Prime XBT - mainly because I like trading with leverage and shorting (Bitfinex offers 3.3x leverage and PrimeXBT offers anywhere from 1x to 100x).
Bitfinex provides a greater selection of altcoins and pairing options, has good liquidity, and is reliable. Whereas, because Prime XBT offers such high leverage it only features the top 5 in market cap - being more predictable, thus less risky. It also has excellent liquidity and is reliable. These things are very important to me.
So I’ll typically use Bitfinex for bull runs and higher risk trades (more obscure altcoins), basic ‘buy low - sell high’, and Prime XBT for bear and sideways trending markets to maximize small price movements.
Both offer advanced trading strategies, tech analysis tools, and a highly customizable UI. Prime XBT’s platform is the easier one of the two to use, however, less experienced traders should opt for lower leverage, to begin with as they develop their skills.
Bitfinex fees are fair, between 0.1% to 0.2% (the more you trade the lower the fee). Prime XBT takes a flat fee of only 0.05% on all trades and all assets.
Possible restrictions for Bitfinex: they do require KYC and a minimum deposit the equivalent of $10,000 USD to use the platform - which can be difficult starting out. Prime XBT: no KYC and their minimum deposit is only around $5.