depends on what you want. Massive would be better for bass and lead sounds. Where absynth is better for pads. If you are going to be making electro, glitch, dubstep or harder forms of dnb, I would go with Massive. If you are going to make trance or ambient/chill/lounge/liquid dnb, I would go with abysnth.
They would probably be awesome compliments. Then again you could get a synth like scanned synth by humanoid sound systems for donationware, and use it for dirty bass sounds!!!