With only triodes in the chain, and without multistage fb, transformer coupled has certainly some advantages over capacitive coupling.
Alone the fact that the "gridresistor" can be the low Rdc of the secondary winding is a big assurance against possible tube runaway with neg gridvoltage biasing.
Downside is mainly price, weigth, increased capacitance, phaseshift, ďelay, increased distortion do to the
decreased loadimpedanz and therefore Increased loading at the frequency extremes.
20Hz transformer distortion will propably be of little concern because it will be swamped by speaker distortion. But one should not look at the 20Hz thd alone without considering the harmonics
intermodulation with themselves and the audiosignal, things are more complicated than comparing 20Hz speaker distortion with 20Hz amp distortion.
There is no way around the fact that a transformer means addional reactive loading of the amplifier stage driving it. lncreased loading means decreased voltage swing and/or increased distortion, simple as that.
In that regard, cap coupling has an advantage, at least up to the max Ub the tube can handle or the ps provide.
Same goes for chokes, alltough in my opinion, the advantages of semiconductor CCS easely is not what is often presumed, the high impedance at dc can be a far cry of the real impedanz at higher frequencies. Additionally, circuit depended, the voltage modulated capacitance, especially with a semiconductor ccs, can become a problem during high voltage excursions, and chokes could be an overall better choice.
As always, multiple choices, each has its own strength and weaknesses.
So yes, transformers and chokes are simple to apply, but anything else about them is not simple at all.