Hi Westhill,
A 64' pipe playing low C produces sound at 8 HZ, or 8 cycles per second. The human ear can only hear down to about 20Hz. What establishes the note that we "hear" are all the upper harmonics ... the rest is "felt", if we were to be in the same room where it is being played, or the sound is reproduced on a "killer home AV system."
The two 64' ranks mentioned are at extremely high wind pressures ... they would hardly be used for mp situations. On the other hand, there are softer 32' stops, for example the Untersatz, which lends itself well to the softer combinations used in the pipe organ.
The 64' stops, is, imho, a novelty item ... there is some organ literature that specifically calls out for a 64' stop. Not one single pipe organ where I live has a 32' rank, but we organists are still able to play those pieces that suggest using such a stop.
Is it a question of 'mine better than yours' ? I don't think so ... Heck, if one has the $$ to spend on this rank, all the better. For most church organ budgets, even a modest 32' pipe rank is totally out of the question.