is there a difference in stopping power between brands like jagwire and tektro/trp, and kool stop and swiss stop?
assuming comparing correlating pad material

I don't know that there is any actual testing of such. Might be some biased studies by the individual brands of such and maybe some biased articles of bike mag's that depend on advertising.

Certainly everyone thinks the brand they buy is the best.

I just get the pad that is made by and recommended for my brakes by it's maker/brand.

Always get the ones with the venting ridges to prevent brake fade due to overheating. If you live on the flats, don’t worry about it (since you don’t post your location)

just watched this the other day.

Yes, better pad compounds and backing plates make a difference. Kool Stop or SwissStop are the way to go. I think pretty much all of my bikes are running KS brake pads or SwissStop these days except for some Shimano pad with the cooling fins but KS has those so eventually they will swap out especially since the red would look nice on that particular bike.

Having used cheap pads I felt a difference and then having used KS pads I noticed a very positive braking and maybe a little better life but I did no scientific testing on that so and I did wear out a rear brake on a bike a little faster but have since evened out my braking on that and solved the issue.

I never had problems with Jagwire brake pads they stop just fine and most bike shops have them in stock.

Or, they think what the conventional wisdom says on Bikeforums and other social media is the best. A bunch of random enthusiasts with no actual controlled experience, or even much of a variety of experiences use strangers' recommendations and it feeds on itself - not knowing any better we all tout the ones we have used, because they work fine. I'm guilty to a certain extent, and note, I'm not saying that al the personal recommendations made online are BS, just that there's generally no reason to think they're the best recommendation.

I get what's easy and economical to get online, or get what's available locally the day I need them, or most likely, do what you do - get the brake brand's pads, rim or disc.

"Stopping power"??? Any pads from any brand will be able to lock up your rear wheel and/or throw you over the front wheel, provided your brakes are adjusted properly. Which means that you will always have all the stopping power you can possibly use (and then some).

Stopping power is never an issue with bicycle brakes. There's no reason to worry about it. Unless, of course, you are talking about some special kind of vehicle, which is, say, unlikely to flip over (e.g. cargo bikes, recumbents etc.)

Don't know about stopping power but the only pad manufacturer I've had actual bad experiences with has been Kool Stop. It's the only pad that has suddenly just gone and dropped the friction material from the backing plate. Could be a fluke but it's not fun when that happens.

Sintered pads offer the best stoping power. Harder on rotors but you gotta stop.

my 2 DB bikes see almost all of their miles in Vermont.
steep, sometimes twisty, and/or technical class-4 road, not too long descents, that often times require a rapid deceleration.
i find myself having to apply continuous grip on the levers for quite a while to keep speeds low, because of steep, twisty, technical conditions.
i don't ride in wet weather

This was my first thought. However, before posting your exact sentiments, I concluded that "stopping power" wasn't necessarily meant as a technical term and might include various other aspects of brake performance. Problems sometimes arise in internet forums when people understand language differently.