Biggest benefit is Photos is supported and has a future and iPhoto was discontinued over three years ago, has not been updated since and never will be and some day with no warning with some upgrade will totally stop working so it has no future at all.
Beyond that there is the fact that Photos is more stable, have more features, integrates with Apple products better and is gully supported with new releases several times a year each with many bug fixes and many new features
In short iPhoto is dead and Photos is alive and superior in nearly every way to iPhoto - it is a totally new program with a learning curve and requires new workflows - these links cover some of the differences and have suggestions for a trouble free migration - : Links to User tips re migrating from iPhoto to Photos
LN