I'd personally go with FTX as it's pretty much the one that has shown the least sort of "shadiness" compared to the other two. Binance is the biggest, yes, but it's pretty much always in the legally gray area; pretty much the exchange that has likely pissed off a lot of regulators.
Why is that?
Because..
https://cryptosec.info/exchange-hacksThis is true, The real reason why Sam of FTX decided to part ways with Binance partnership is because Binance don't to follow the law and just contented on dodging the law by changing there headquarters location regularly. I don't know about Kucoin but FTX is the one showing cooperation to the law and happily complying with it. I trust Sam and most of the project that they are working with like Serum and Solana.
My vote goes too FTX too.