VPAP AUTO 25 vs VPAP ADAPT SV

I have been successfully using my RESMED VPAP AUTO 25 since 2009 and have an opportunity to acquire an RESMED VPAP ADAPT SV machine which seems to be a newer machine. I like the AUTO machines and am I correct that the VPAP ADAPT SV is not, and just runs at a set pressure?

The Adapt SV is a totally different machine from the VPAP Auto 25.
The Adapt is what is primarily used to treat central apneas but it will also treat obstructive apneas and the pressure does indeed fluctuate...and it can fluctuate a lot depending on the settings.

I assume you aren't talking about the S9 models but instead talking about the older models based on either the S8 or S7 series line?
Unless you are not in the US...I don't think they use the term "25" with their VPAPs anymore.