While there are many reliable crypto exchange platforms, I'll tell you about the differences between the most common ones.
Kraken.com: Which has a good customer support and always responds within a few hours.
Binance.com: Is very low-fee with 0.1% fixed and widest choice of altcoins, so when they are added to the main site like coinbase, you can enter them before going up to 10X. US residents use fewer coins, binance.us, instead.
Coinbase.com: There are no great coin imo options on Coinbase.com, but it is always getting better, easy to sign up in the US, ideal for beginners.
Investvoyager: Also has some altcoins such as AVAX that are not found in any of the above.