I don't think you'll find an exchange that works 100% perfect... GDAX has probably been the most consistent for me but...
- Some exchanges don't have the coin you're looking for (GDAX doesn't have Ripple).
- Most exchanges can't keep up/predict the volume of new users.
- Keeping up with the increasing volume is hard work so their customer support lags behind.
I currently prefer Kucoin because of the potential of dividends from their exchange coin, but they are currently down most likely due to volume issues. They have been getting a lot of new users/chatter lately.