Raspberry Pi vs BeagleBone torrentbox
The Raspberry Pi will do everything you need, and I can't imagine the BeagleBone being any simpler to set up. All you do is flash an SD card (with the very simple Win32DiskImager in Windows, for example), plug it in and SSH to it. Or use the HDMI port with a keyboard if you prefer.

Are you plugging the 4G dongle directly to it? If not, be aware that the Ethernet port is limited to less than 2MB/s due to the very weak power regulators on the Raspberry Pi.