600 has RF CH 3/4 out, but drops component, optical audio, UHF remote, modem, and front panel display.
The 605/630 have the same connections/display/UHF remote.
It has component, optical audio, eSATA, modem, full display, UHF receiver/remote. The 630 has two tuners and a built in HDD.
All have brick power supply, satellite coax in, composite RCA A/V out, HDMI, Ethernet, USB, and 3.5mm serial port.
The 600 and 605 use exactly the same software, so operate the exact same way.