In many ways your question is really about which sounds better, your
average tube vs. your average solid state amp, whose output vs.
impedance profiles are as you describe, and there's no simple answer to
your question in terms of which is preferable.
We can usually assume that an amplifier that does not double it's power as impedance drops has higher output impedance. This is not always, inevitably true, but mostly true. Sometimes an amplifier can maintain a flat frequency response any time you stay below it's maximum output, though this tends to be rare, but possible with high enough feedback.
When an amplifier has high output impedance the frequency response changes from flat to one that looks like a speaker's impedance curve. That is, the impedance curve dominates the amplifier's output. Take a look at any tube amp measurements from Stereophile which uses a simulated speaker load to see what I mean. Here's an example:
https://www.stereophile.com/content/cary-audio-cad-805rs-monoblock-power-amplifier-measurements
The squiggly black line is the output changing from flat-ish to the speaker impedance.
Is this bad? Meh, depends. Sometimes you get a great combo that really colors the sound in a way you find pleasant. Sometimes it means you want a speaker that has a really flat impedance curve (like Fritz) so it can be more neutral.
We can usually assume that an amplifier that does not double it's power as impedance drops has higher output impedance. This is not always, inevitably true, but mostly true. Sometimes an amplifier can maintain a flat frequency response any time you stay below it's maximum output, though this tends to be rare, but possible with high enough feedback.
When an amplifier has high output impedance the frequency response changes from flat to one that looks like a speaker's impedance curve. That is, the impedance curve dominates the amplifier's output. Take a look at any tube amp measurements from Stereophile which uses a simulated speaker load to see what I mean. Here's an example:
https://www.stereophile.com/content/cary-audio-cad-805rs-monoblock-power-amplifier-measurements
The squiggly black line is the output changing from flat-ish to the speaker impedance.
Is this bad? Meh, depends. Sometimes you get a great combo that really colors the sound in a way you find pleasant. Sometimes it means you want a speaker that has a really flat impedance curve (like Fritz) so it can be more neutral.