There's a detailed comparison between versions here for Android:
http://skysafariastronomy.com/produc.../versions.html
and here for iOS:
http://skysafariastronomy.com/produc.../versions.html
Personally, I can't see any "must-have" features missing from the Plus version, so that is what I went with. I figure there are more than enough objects in the Plus database to keep me and my 200 mm scope satisfied for a long time. Plus has the telescope interface built-in, so I figure there's not a huge amount of value in being able to "Go-To" an object that my telescope can't see or image.
(Even if I started working my way through the 31,586 DSOs in the Plus version at the rate of 10 a night, that would take me about 10 years - not allowing for any cloudy nights! When I run out of DSOs, I can start ticking off the 2,637,791 catalogued stars at the rate of 100 a night for another 72 years of observing.)
Seriously though, having access to the "Complete General Catalog of Variable Stars" and "Complete Washington Double Star Catalog" in the Pro version might be a "plus", if that's your passion, but there are plenty of variables and doubles catalogued in Plus.
The Hi-Res images and Moon map in Plus are "nice-to-have", but this imagery is available on-line anyway.
Be aware that the developers don't offer an upgrade path, so if you think "buyer's remorse" might ever be an issue, go for the Pro version.