First of all the package server is used to distribute packages for the WCF. It can be abused for a download system but I wouldn't do that.
Zitat1.- Files will be upload only by me, so this is simple
That's possible for both products, because both use the permission system.
Zitat2.- Download access to specific usergroup(s) at least in category limit if not per file.
This is currently only possible for the package server. Nevertheless user have to authenticate on the package server first before they can see/access the packages. This feature will be implemented within the next feature update of the webdisc, which I'm currently working on.
Zitat3.- Limit downloads per day or any other time frame (eg per week).
It's possible only in the webdisc. There are user based and global traffic limits (but not on the amount of downloads). I will implement an amount based limitation within the next feature update. The package server will not have any of these limitations.
Zitat4.- Paid downloads (???). I know that this is not a common features, but at least will helps me to bypass the missing "Subscriptions" from WBB.
This is not possible in both products. If you want that feature you have to buy the customer area. This products also has the option of free downloads. Maybe that product is an option for you?