Quality and performance are the same. Operation is the same (tube-stacked blowbacks). The only advantage to Azodin guns is the cocker-threaded feednecks (industry standard) and integrated rail into their grip frames (more asa options, as you don't need direct mounts or adaptors or separate rails or anything like that). Keep in mind, it's like you're paying extra for this, as Azodins cost more.
The Azodin Zenith in particular does have one feature that spyders do not have, and that's the ZeRO system, or Zero Recoil Operating system. It's just an externally adjustable valve system, letting you control the valve timing. However, it's not something newer players should be messing with and nothing you necessarily need to adjust all the time. Basically, once it's set, don't ever touch it again - for that reason, i think it's pointless having that option. The same result can be obtained on a spyder by simply buying a spring kit, and any spyder + spring kit is cheaper than the Zenith.
Don't get me wrong, i like Azodin, and i like the innovations they've taken into separating themselves from other companies that make similar guns (Spyder, Piranha, etc), but don't assume that they're BETTER than those companies.