Many boards are actually better then the pi. The only reason we offer the pi image is that so many use it and have it.
Pi is just slow with lan/usb. For the different board is just important to have a debian like linux distro running on it. But you will face the same problem with the dell. There is no convenience image with webcam, network, usb mount so you have to configure these your self.
You can use the pi image a bit to help you get started. All these scripts are under /usr/local/Repetier-Setup - binaries in bin subfolder. So it is possible to extract the webcam stuff, but that is also described on our homepage.
ffmpeg can be downloaded on their homepage if it is not included in ubuntu. Alternatively just use avconv whcih is also supported.
