When Bisq 2 is launched it will initially only use the one trade protocol 'Bisq Easy' therefore the differences are based on a 2-of-2 multisig protocol (Bisq 1) vs a reputation based trade protocol (Bisq Easy).

What is Bisq Easy?

Bisq Easy was designed for new Bitcoin users who have not yet purchased Bitcoin and thererfor cannot use Bisq 1 due the requirements of the security deposit. A lot of effort was put into making it as simple to use as possible.