First point would be the platform's reputation. You don't want to go where there are problems or high delays in handling various issues, including the deposits and withdrawals.
Then the liquidity on the trade pair you want should be at reasonable levels.
The fees - trading and also deposit/withdrawal - are quite important too.
After this I think that's all personal choice. Some prefer the ones where KYC is not needed, for example.

You should also be prepared to see a lot of annoying trading bots wherever you go. In some places they may be more or less annoying, you'll have to look around for yourself.