Bisq is a "Second layer protocol". To use Bisqm you run a software program (Bisq client) in order to transact.

RoboSats, on the other hand, is a website. Yes, it is a website that can only be accessed via Tor (for transacting, at least) or I2p, but it is still just a website. If that website goes away, you cannot continue to use RoboSats.

Though both Bisq and RoboSats have escrow methods, .. those escrow methods for each are non-custodial. i.e., meaning the platforms don't exclusively hold your coins. Bisq is on-chain and implements escrow through the use of multisig transactions. RoboSats uses Lightning network and implements escrow through the use of a "hold" invoice.

Bisq is therefore considered an exchange that is more decentralized than is RoboSats as Bisq is a protocol.

But RoboSats does a fine job of eliminating the problems of a centralized web-based exchange. RoboSats uses Tor, so even they don't know your IP address (albeit, they could serve up javascript at any time that does collect that info). RoboSats uses PGP encrypted chat messages, so even they can't know the payment instructions provided by the seller (unless that info is shared with them by one or both participants of the trade, such as for dispute resolution). But again, being a website, they could easily add some javascript code that does collect that chat info, for just specific users even, so that still requires a bit of trust extended to RoboSats. And even the concept of a user ... RoboSats is designed so that you use a new identity (robot) with each trade, which increases the difficulty for an observer to figure out which traders on the platform are the most active (which a government considering a crack down on P2P trading by doing sting operations would want to first learn.)