I've not tested potassium bicarbonate and sodium bicarbonate waters head to head. There isn't a reason to suspect these cations are doing anything special in terms of extraction which leaves the flavour they contribute directly. Both are salty. Most people prefer the flavour of sodium as potassium can have a slight metallic tang to it. I have a hard time believing you could tell the difference in coffee. In fact, the concentration of Na ions in most recipes is at or below the threshold of perception in water, FYI. Source: https://www.waterboards.ca.gov/waterrig ... s/II_7.pdf see Table 3.

Of course, I'm a longtime lurker so take my opinion with a grain of salt.

I recall that Dr. Robert Pavlis has pointed out that coffee contains much more potassium than sodium, so it would appear that a little more potassium would have little if any effect upon taste.

Makes sense. I think the choice between the two is splitting hairs, personally. Pick one. It's not going to matter in the finished product.

maybe one good reason to choose the potassium bicarb then is lazyness

it's ~100g/mol, which makes it a lot easier to calculate concentrates and recipes...

Theres value in laziness; the categorical best way to do things is often not consistently worth the effort (diminishing returns, etc.)

For example, I tend toward sodium because I always have baking soda on hand and I avoid comments from my spouse about turning into Walter White.

Totally understand you. I'm already past the Walter White test though. When I started roasting coffee and messing with phidgets, thermocouples, anemometers, variacs, precision scales, she had her chance to question it. But then when the coffee results started showing up and I continued poor, she noticed there was no side business...