CoinEx or KuCoin?
If this is only your choice, I prefer to use Kucoin. Though I didn't use this crypto exchange so far here, the good thing is, I don't see a serious problem with them. So, therefore, considering they are good exchange AFAIK. Upon having short research I found this exchanger comparison between them. As you can see, technically, Kucoin has a better advantage than Coinex in the stats shown.
Remember that there are pros and cons between a centralized and decentralized exchange, usually, DEXs are low volume that could be it takes your order so long to execute. However, you can find a lot of DEXs here and have your own research before choosing one.
https://coinmarketcap.com/rankings/exchanges/dex/
