I believe that Ralph has pointed out in the past that using the higher ohm tap results in less distortion, increased bandwidth and better efficiency.@charles1dad Actually what I've said is that all amplifiers (tube or solid state) make less distortion into higher impedances; in the case of tube amps you also get wider bandwidth and greater efficiency.
Another way of putting this is if high quality audio reproduction is your goal, your amplifier dollar investment is best served by a loudspeaker of higher impedance- 8 ohms as opposed to 4 and 16 ohms as opposed to 8.
An additional benefit of 16 ohm loudspeakers is the speaker cable is far less critical for proper system sound whereas at 4 ohms its critical!