Well i would say they are the same.. The only way one can be better is if the Solenoid opens faster than the other brand
The jettings are the same for each Kit. They go by numbers which are universal for any nitrous kit.. All a nitrous kit consist of is The bottle-Nitrous Line-Solenoids-more nitrous line-nozzle-jetting-into the intake...
Now the only part where brand would matter is the Solenoid Part.
It opens and closes whenever u hit the button.. And the type of nitrous u have only depends on where u get it from.. So i would personally say that all kits are basically the same!
Besides Zex :-X
All of the zex's kits are built into one command center which controls everything.. It monitors the fuel pressure to insure the right amount of Nitrous going into the engine..
This may be good or bad.. I remember once a shop telling me the Zex is somewhat a Imitation Nitrous kit.. Because its for beginners and that the nitrous level its going to shoot wont be as nominal as other kits...