Q: iPhoto v Photos

You can use iPhoto for example to add location meta data.

Until your absolutely sure Photos will suit your needs, I would not delete the iPhoto library or application from your hard drive.

Photos is lacking many of iPhoto's features (like multiple sorting options) which might impact how you use it.  This User Tip highlights the differences between the iPhoto features and those in Photos:  Photos 2.0 vs iPhoto 9.6.1:  Features and Capabilities.

You can still use iPhoto if you have iPhoto 9.6.1.

And keeping the iPhoto Library won't use up extra space on your hard drive: Photos saves disk space by sharing images with your iPhoto or Aperture libraries - Apple Support