My list of importance goes something like this:

1. Good liquidity
2. Good platform speed- I don't like trading on Bitmex especially when things are moving fast and their platform occasionally overloads, which can result in high slippage or losses.
3. Good reputation- This could be tied with #2, but I am always wary of very new sites offering derivatives as some of them could just run off with your funds with no warning.
4. Easy-to-use interface- You trade best when you're familiar with an interface, so it's important on newer sites that the interface is similar to existing ones on more popular sites (like Deribit and Bitmex), or it's just designed to be quick to learn with proper documentation.

I don't ever use high leverage, and mathematically it just doesn't make sense to use insanely high leverage like 100x or 200x, so the availability of very high leverage is just clickbait to reel in newbie traders IMO.

I value the security of funds more than quick withdrawals, which is why I trust Bitmex more than some exchanges with my funds, but at the end of the day there's no way to tell how an exchange is keeping user funds, and any exchange could potentially have a serious security breach involving the loss of funds at any time.