new / old iPhoto

Which iPhoto versions are you referring to?

Apple stopped the development of iPhoto. So there is no iPhoto 2016. Instead of iPhoto we now have the new Photos for Mac application, that will come as part of MacOS 10.10.3 or later.

It is very different from iPhoto '11.

If it is bitterer not will depend on whether the differences suit your needs. I like the new Photos for Mac a lot, because it supports iCloud Photo Library. It is easy to keep my Photo Library in sync across all my Macs. Previously it was a pain to work with one library on different Macs.

Sorry but there is no new iPhoto - the latest version of iPhoto is 9.6.1 released well over a year ago

There is a totally new program called Photos

I like it because of the ability to have the same library on different devices and much better editing

It is different

here are some differences

Photos 2.0 vs iPhoto 9.6.1: Features and Capabilities

and some info on how the migration works - How Photos handles content and metadata from iPhoto and Aperture - Apple Support

and suggestions on preparing for the migration Notes on Migrating an iPhoto Library from iPhoto to Photos for Mac

LN