Simple answer is quality.
Let's start by going through the list of features you gave.
FREE SETUP in less than 24 hours!
Setup had better be free! Ours is typically 5 minutes or less.
FREE 5-man TeamSpeak Server
We currently give a free 16-man Ventrilo server for each 14-player and larger game server.
Complete Server Control Panel
Ours is a bit better.
24/7/365 Server FTP Access
Fluff, since every provider should have this.
Unlimited Space For Mods/Skins
We offer 2 GB, and more if requested. We've never shut anyone down for using too much space.
Unique Server IP Address
We pioneered this feature.
Server Listed on G-Spy & ASE
Fluff. Those services get the list from the game's master server, so any provider can say this.
FREE Sub-Domain Web Space
As do we.
PsychoStats Available
We not only have them available, but they are free.
24/7 Unmatched Support
Our support is not strictly 24/7, but you won't be able to tell that from the quick responses. We offer support through chat, email, and these forums, and as you can see here, our staff is extremely knowledgeable. I'd argue we have the best support in the industry.
If you're looking for a list from us, we have one here:
http://rentals.nuclearfallout.net/rent.php?content=main.
One important thing about our servers is that we use the fastest available hardware (currently dual Woodcrest 5160 machines) and bandwidth (InterNAP), a very powerful combination that you'll have difficulty finding anywhere else. We also have insanely high levels of automation, such as load-balancing systems that keep every machine running smoothly and underloaded.
To get the best impression of the differences here, I'd recommend trying both services for a month. Take advantage of the customer support, ask your players how the servers feel and what their pings are like (not everyone will get the same pings to both servers as you do), and keep track of how often the server is down. I'm confident we'll come out on top, and worth the extra $7 per month.
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. In two days, if you are satisfied with the server and do not cancel it, the subscription will charge.