Quote from: MedvedTrader on November 04, 2017, 08:48:24 PM

GDAX is very high-volume, US-based and pretty reliable.

I use GDAX, but I would call it anything but reliable. The API and trading engine tend to drop out during high volatility, so it can be a terrible place to exploit intraday volatility. I've sometimes been locked into losing positions due to their frequent downtimes.

Quote from: captianjojo on November 04, 2017, 08:16:59 PM

I was wondering what exchange will let me buy/sell bitcoin quickly so I can do day trading.

None of the exchanges are without their problems. I'm weary of Bitfinex because of their interaction with securities and lack of licensing, and also because of the still-unexplained "hack" last year. GDAX and Gemini are okay, but liquidity is not ideal and they are both prone to downtime. Kraken is very unreliable and is also an unlicensed MSB.

Bittrex and Poloniex both offer lots of altcoin and USDT markets, but no actual USD markets and both platforms have a high rate of complaints if you look into it. Bitstamp is probably one of the most trusted platforms (along with GDAX and Gemini). I'd rate their trading engine and liquidity as average. Regarding fees, your best bet is GDAX: no fees for maker orders. There are high fees for market orders, though, so don't use them.