Google Earth Plus features the following enhancements:
Faster performance - enhanced network access
GPS data import - read tracks and waypoints from select GPS devices
Note 1: Verified support for Magellan and Garmin devices only
Note 2: Does not support export of tracks or waypoints to a GPS
Higher resolution printing - greater than screen resolution
Customer support via email - not just website
Annotation - draw outlines and shapes
Import - read address points from .CSV files
Note: The free version of Google Earth, Google Earth Plus and Google Earth Pro all share the same imagery database. Purchasing Google Earth Plus will not improve the resolution and age of the imagery; however, you will get additional capabilities and features.
Before you purchase, you may want to use the free version of Google Earth to view the satellite imagery of the area you're interested in and determine if it appears blurry or out of date.