Well for starters the product is smaller and not that extendable. So it means when typically with on-prem you start developing and customizing the software to fit it into company procedures then with Saas ERP company needs to fit into ERP processes.

The UI is based on HTML and therefore users like it more and are not that hesitant to start using it and less training is needed.

Public API-s that you can just take and make integrations, no need for allowing access through firewall etc.

There are many more but these are just some that I can think of right now.