AWS Personalize: Difference between, E-commerce recommenders: Recommended for you & Custom Solution: User-Personalization recipe

The main benefit of having Recommenders vs Custom solutions is akin to the difference between hosting an API on Lambda vs. EC2. With Recommenders, you get an out-of-the-box managed solution that manages retraining with built-in filtering for already bought items. Custom solutions allow customers to manually manage their model updates and retraining at their own cadence. The underlying recommendations with the same data would be similar but the managed experience as a whole is what makes the difference.