Both new Minis also comes with FireWire 800 port, 4 USB 2.0 ports, and an SD (Secure Digital) card slot. I find that an interesting combination of ports. First, the inclusion of FireWire makes it clear that all the rumors over the last two years that Apple was abandoning FireWire were false. I think that's underlined by the fact that Apple is including USB 2 support, but not the far faster USB 3.0.
For networking, both use Gigabit Ethernet and the usual assortment of 802.11b/g/n Wi-Fi support. And, for that wireless keyboard and mouse, Bluetooth 2.1+EDR.
The desktop Mac Mini comes with a 2.4-GHz Intel Core 2 Duo processor and a 320 GB, 5,400-RPM hard drive. It also sports a slot-loading SuperDrive optical drive. Apple will upgrade these for you if you want. But, another reason why I see Apple still missing the bus when it comes to home theater is that a Blu-Ray drive is not one of the options.
The server Mac Mini doesn't have a slot-loading optical drive. This rather bothers me since there are still times when I've needed to load software on a server from a CD or DVD. It also gets in the way of using this one for a pure media server since you can't load DVDs into it for conversion with HandBrake into a digital video library.
By default the server Mac Mini comes with a 2.66-GHz Intel Core 2 Duo CPU and two 500-GB, 7,200-RPM hard drives. You can either use this for a combined 1 terabyte of storage or, the smarter move for a server, mirror the disks at RAID (redundant array of inexpensive disks) level 1 for better data security. If you need more storage, and for a server you probably will, you can attach external hard drives.
It also comes with, besides the usual Linux and Unix server tools such as Apache for Web serving and Samba for Windows file and print sharing, Time Machine backup; Wiki Server, Mac OS X's groupware software; and Podcast Producer, a full-featured pod- and video-casting production program.
Last, but not least, if you don't like shelling out money for Windows Server style CALs (client access licenses) it can support unlimited clients. While you can certainly put together a cheaper department or SOHO server with generic hardware and the Linux of your choice, I'd certainly consider this server for a Mac-centric office.