Bitfinex offers what is a most for any real trader, liquidity. A big amount of pairs and you can sell any single one of them fast. If you encounter any issue along the way that might slow you down, the support gets it fixed fast. The UI could use a little more love, as some features are out of the way and a bit hard to find making you lose a bit of time learning it before you jump into trading. Still one of the most efficient platforms for cryptotrading.