Pentode Power Tubes - Ultralinear vs Triode

My experience is that when an amp is designed with a switch which literally alters the circuit, there is some compromise in one of the circuits.  If the amp is setup primarily for Triode, the tetrode/pentode circuit won't sound as good as a pure circuit designed that way.  Ultralinear seems to be an exception.  

Generally I prefer triode couple amps.  I am currently running Art Audio Opus 4s with KT120s (also runs KT88s) and I love them.  They don't offer a switch.  Tom offers a Triode couple (45w) or Pentode coupled (75w) amp but no switch because the switch forces a compromise of one of the circuits.  

The McIntosh MC275 is a pure pentode circuit for either KT88 or 6550 tubes.  It sounds as good as many triode coupled amps I have heard using the same tubes.  

Alternatively, I have had amps in the past and found that the Triode circuit would sound great and although it delivered more power, pentode/tetrode would sound muddy.  I thought it was an inferior circuit yet you hear the MC275 and that is clearly not the case.  It is the switching process.  

Ultralinear seems to be an exception.  Tubes in Ultralinear sound...well, linear.  Tight bass and extended highs.  Sounds SS to me frequently.  I find this unappealing as I purchase tube amps to sound like tube amps.  If they sound SS, then all I am getting is an amp that costs more with tons of maintenance.  

op

answer to your question is totally dependent on speaker and its load to the amp

triode mode reduces output 3 db which is substantial on some lower sensitivity speakers and also changes the power tubes' 'leverage' into driving the speaker

so as is the case in many of these questions, you can really only try for yourself and see

DPHP user here.

Check out the KT77 is you like the EL34 sound. To my ears they are a little more dynamic overall. Look at KT88 for more on the bottom end at the expense of less midrange magic.

 I have been using the old RCA 6l6G coke bottle in my PL. They are a lower power(different from modern 6L6). They are a close enough combination of EL34 mid and KT88 dynamics.
One of the few NOS American power tubes still available for a reasonable cost.
https://www.ebay.com/itm/RCA-6L6G-Smoked-Glass-Tube-NOS-foil-twin-D-getter-copper-grid-posts-code-35...
They have a "dry"sound which to me is more convincing compared to the "lush" EL34 tone.

I prefer the triode setting most listening sessions. A flat recording sometimes sounds better in UL. You are aware of the 2 innermost preamp gain tube also will fine tune the sound? Subtle, but another tweaky option.

Be an early adopter and try the KT170
https://primalunablog.com/2020/10/30/tung-sol-kt170/
They should be like a supercharged KT150, which already is a powerful tube. I haven't tried them in my amp yet. 8=$$$$