I personally like Bitfinex the most. It has the best features because it allows for margin trading and short selling so you can profit from bitcoin either direction. I also like the potential of the new exchange coinsetter but the withdrawal times are much longer than BFX and they haven't added leverage trading yet.
I've mostly given up on altcoins as a waste of time compared to bitcoin. Even litecoin I don't value very highly due to the vast majority of scrypt miners flooding the market and devaluing the currency.