Official Website offers updates, map editor/maker, and little tid bits WITHOUT paying/registering/signing up for anything.
Soldatmods.tk offers different weapon skins, interface skins, "gostek" skins(player model) entire mods maps, map makers. Just about anything you want for soldat.
The only thing you get for donating is:
1. A star next to your name.
2. Colored jet flames.
3. Custom music.
4. Official interfaces.
P.S. There are only 18 weapons, mods only change the way everything looks, weapons, people, explosions, etc...
The stuff on the community site have about 20 extra weapons (all unique) different kinds of bots, about 10 new maps, and a few dozen new modes.
I don't understand how you didn't get that if you registered, you get an E-mail that gives you a username, password, and link to the site.