There are hundreds of Bitcoin exchanges which anyone can sign up for and start buying Bitcoin quickly and effectively. Personally, I use Gemini or Kraken. Gemini has an excellent interface and low fees, while Kraken offers some of the best crypto assets and is one of the oldest exchanges in existence.
The real question is... What is your favorite Bitcoin exchange?
The two exchanges you have mentioned is not my favorite exchange though there are good and among one of the bests exchange in cryptocurrency market. Poloniex and binance remains my bests exchanges and I do used them for trading. I like poloniex because that is the first exchange I opened account with and up till now I am still tradings both arbitrarily trading and margins trading through there platform.