Is that a Dreamstation, I have no idea what a REmstar auto 560 is. In Australia its probably known by something else, different number etc.
We have end of financial year sales at the moment, so shopping for a discount. There was a whine or hum in my mask above 7cm , wondering if its a seal or bearing in the Resmed 50 series one machine. Tried everything, put blanket under machine, new filter etc. Maybe its the mask but I think a vibration is travelling up the hose going into the mask. I tried earplugs it made it worse, the hum or whine echoes in my head. Tried it for 4 nights , took mask off and said no I think I need a new CPAP machine. I even took it to the shop they couldn't hear what I was hearing.
This CPAP is all new to me so hopefully a new machine will be the answer.
The 50 series one machine is a Philips Respironics machine not a Resmed.The older designations for the Resmed are like S9 autoset or S9 VPAP Auto etc. The link that Opalrose gave will give you a good idea of the naming conventions (or should I say variable naming conventions).
Echoing others comments it basically comes down to preference and perhaps pricing. I use the Resmed A10 (some call it the S10) and it is extremely quiet as long as the humidifier is properly seated in the chamber which is not hard to do. It also is light so travels in its case easily. Given that I found it unnecessary to purchase a separate travel unit so i can have the same sleep while away from home. There are very small travel units available but they have reported issues (see other threads re the Z1) with noise and turning off randomly to name a few so the light A10, at least for me, killed two birds with one stone.