The Audio Gods are tough but fair-Have you had the "Curse of the 300B" ?

These amps can really pull you in to hear the singer. The voice instrument is so spot on it can provide moments of disillusionment. For example, I've always preferred Sam Cooke's Live at the Harlem Square Club over Live at the Coppa.  The former is way more free and pushes the R&B needle.  It's musical and soulful.  On my 300B setup I agree with that but I also can put Live at the Copa on and be drawn in... in so much that I start enjoying that album as much as Harlem Square. My attention gets focused on the music and not that this isn't my favorite Sam Cooke album.  And I start hearing and feeling things in the vocals that weren't present before. It's wonderful in the truest sense. 

The 300B SET also delivers smaller group instrumentals like no other.  Drums in the jazz, acoustic/folk settings are sublime.  You really identify the drum skins. You do this sonically more than viscerally.  It is, however, intoxicating.  

When done right these amps can be captivating.  But the 300B mistress is not without its issues.  

-You have to mate it with more sensitive speakers.  This is huge.  You are no longer looking at the lion's share of state of the art loudspeaker reviews.  No. You are searching for sensitive, efficient speakers because the 300B runs out of gas real quickly. 
-You have few choices in amps, 
-You have few choices in tubes and they get really expensive for the 'premium' makes.
-You are likely listening at below moderate to moderate volumes. 
-You may keep a second system to use outside of 300B time. 

When I go back to push pull, or even solid state, I immediately appreciate the power and increased visceral impact.  My attention, however, gets more easily lost, and while they don't sound "bad", I lose the clear window into pieces of the performance.  Subtle nuances of how the singer's voice has personality arising out of the phrasing and tone of the vocal.  Instruments with the 300B sound more "instrumenty".  I don't consider any of what's lost when switching to push pull to be hyper detail or analytic.  Instead, it's characteristics of the sound that aren't there leaving less of the inherent personality of whatever sound is being reproduced--vocal, instrument, or the room in which the performance is taking place.

And so I've done things with my system to help it when it's in 300B mode and push pull mode.  For 300B, I added an REL subwoofer and a second Sumiko I had laying around.  I use those to load the room and expand low end but increase soundstage and make things sound bigger with few watts.  For the push pull setup, I've got the input source all tube whether digital or vinyl.  

This leaves me with the feeling that the Audio Gods are tough but fair.  It's hard to have it all with SET or PP.  Nonetheless, my mind seems made up that it seems easier to work within the 300B setup to make it better as opposed to the push pull. 

As a total aside, I am not the audiophile sage that many are on this forum or out in the audiophile-wild.  I will say with confidence though that if you love hifi you owe it to yourself to spend a month with a SET amp coupled with efficient speakers.