If you have Maschine and Komplete, that gives Komplete much more of an edge. As for better overall product, that's obviously Komplete since it has a ton of other things while Omnisphere is just a synth. I could go on and on about Komplete, but will instead say that's your best choice if you MUST pick only one. THE OMNIGRID : this is the first layer of the Omnisphere, and it is a distributed peer-to-peer network of computers that deliver computing, storage, and network capacity.
If you know how to work those electric guitar sample libraries like V-Metal guitar and Shreddage II, those with Guitar Rig are very convincing and I prefer the Project SAM orchestral libraries available for Kontakt (Symphobia, Lumina, etc) over EWQL libraries and their "PLAY" format. This award-winning software brings many different types of synthesis together into one amazing-sounding instrument that will spark a lifetime of exploration. Kontakt, however, is my choice for sampled sounds, such as pianos, electric basses (most recently, even over Trillian's basses), and third party Kontakt libraries for orchestral and electric guitar sounds are high quality. If you are into sound design, atmospheric sounds, pads, electronic music etc than this may be a pe. Omnisphere 2 to work correctly all other sounds work in both Omni 1 and 2. Just picked up Omnisphere 2 power synth by Spectrasonics.
I could be a matter of taste, but Massive and FM8 are almost useless to me (sounds are like '80's video game sounds and I don't do dubstep) because Omnisphere covers what I need in their area. This is a bundle of over 4,500 patches for Spectrasonics Omnisphere aimed. Omnisphere is nearly always my 1st choice for synth sounds over the NI synths.
This epic ‘Power Synth’ breaks completely new sonic ground by combining a wide variety of hybrid realtime synthesis techniques, an epic library of remarkable ‘Psychoacoustic. Omnisphere 2.3 is the latest update to Spectrasonics flagship power synth virtual instrument. Komplete has everything while Omnisphere is really just synths and not much in terms of "real world" sounds. After many years of development, Spectrasonics is proud to release the brand new flagship virtual instrument Omnisphere.