Bisq is undoubtedly the king, it has a brutal volume of about 3000 bitcoins per year.

But for a novice it is complicated, I can not recommend it.

Robosats on the other hand is very simple and instantaneous and like Bisq focuses on privacy.

The main difference of use that I give them is the amount of Bitcoin to trade, ie, in robosats orders range from 10 dollars / euros to 4000 approximately, in Bisq the average size of the orders are usually much higher.

The reason is also simple, Robosats is Lightning, and the liquidity of users' wallets is not usually high, for large transactions Bisq is better unless both use Lightning Custodial wallets.