you forgot the most important point "your location" where trading platforms need to prove identity, make sure that your state supported by the platform is the most critical factor before the selection.
Suppose you are from the USA, the best platforms according to my knowledge: Coinbase, Kraken, and Binance.
- security (should not have had any hacking in the recent years).
There is no unhackable platform, and times of hacking or years are not a decisive factor.
Remember: do not keep money in the podium as much as possible