It is not well known, and therefore suprising, but the Orion 565 holds a few advantages over the Orion II 566 in terms of performance:

1. The 565 provides stereo line out connections on the Aux I/O connector where the 566 only has a single line out

2. On very strong s9++ signals where the hardware AGC kicks in, the 565 receiver stays clean but the 566 receiver is prone to occasional distortion. This has been verified on four out of four 566's tested, which spanned the entire production history.

3. Some consider the receive audio quality slightly smoother on the 565

Of course the 566 holds a major advantage over the 565 with its crisp color display and the 566 also seems less prone to the 565's intermittent encoder issues.