Summary
Melodyne 4 essential contains Melodyne's Main Tool for the basic editing of pitch and timing, and offers a particularly simple and economical entry into the world of Melodyne.  If you need more functions, you can upgrade any time to one of the larger editions simply by paying the difference in price. 
Features
Grammy Award-winning Melodyne technology
The algorithms "Melodic", "Percussive" and "Universal"
Melodyne's Main Tool for pitch and timing
Macros for pitch- and timing-correction as well as quantization
Fully compatible: VST, AU, RTAS, AAX, ARA, Rewire
OS X and Windows, 32/64-bit
Requirements
OS X: Intel Dual Core processor (Quad Core or better recommended), 4 GB RAM (8 GB or more recommended), OS X 10.6.8 and 10.9.5 or newer
Windows: ...

Celemony Melodyne Studio4

874.14$ CAD

Summary
Melodyne 4 studio offers you all Melodyne functions for both correction and creative applications on an unlimited number of tracks.  You can edit the sound and musical content of your recordings in such an intuitive manner or make such far-reaching changes with no other audio tool. 
Features
Grammy Award-winning Melodyne technology
All the Melodyne algorithms including DNA Direct Note Access
The full Melodyne toolkit
Unlimited tracks with Multitrack Note Editing
The Sound Editor with its unique capabilities
Macros for pitch- and timing-correction as well as quantization
Precise tempo-detection and -editing
Comprehensive functions for working with scales, tuning and temperaments
Audio-to-MIDI export
Fully compatible: VST, AU, RTAS, AAX, ...