Zex kit is easiest to install.
The wet system is generally much safer IMO. The 'tune' with the fuel jets is easy to manage (straightforward calculations) while a dry system is pretty hit and miss (since you are bypassing nitrous pressure to the vac line on your fpr).
You'll need to set up a WOT activation switch in order to use the wet kit, this is the only plus side the zex dry kit has, you just wire the tps to it and you're done.
I have a really trick little nitrous controller, made by Dynotune nitrous
Link, it's $130 and has support for TPS learning, dual stage control, and window (RPM on/off) functions. You should creep over their site, they've got some really cool stuff...like an A/F gauge that will cut off your nitrous if you start to run lean.