Promotions vs Promotions Engine

Hi,

We are using hybris 5.5.1 and using the legacy promotions module that hybris provides. As we are doing a marketplace implementation where there are lot of complicated promotions, we have almost done complete customization using JALO layer.

With hybris 6.0, promotion engine is shipped which uses DROOLS.

Has someone already used promotions engine with 6.0 and can throw some light on pros/cons with the engine?

Also we will need to understand the effort of migrating from hybris 5.5.1 and using 6.0.

Thanks. Saurabh