Everything that I've read says dot 4 absorbs water faster than dot 3 but has a higher boiling point. Dot 4 needs to be changed more often. The tool I showed above is a handy one as it checks water content in brake fluid to determine if it needs to be replaced or not.

I have found sources that support one or other side. I have not seen any studies (academic) that support one or other point.

My take has been that it's a double-edged sword in a way. If it "absorbs" more water, then less water is prone to accumulate in certain brake components (if possible in a specific vehicle), and that the water becomes incorporated into the fluid, thus requiring more frequent change/maintenance of the brake fluid. And then there are articles which seem to imply that one or the other may induce more moisture into the system. Read 10 article you find on the comparisons, noting the verbage, etc. Also, I believe vehicle usage as far as mileage (total one drives, hwy vs city, normal vs spirited driving, etc.) all come in to play; however, I don't think the average person will notice a significant difference in 3 or 4 with "normal" vehicle use and driving habits.

Also recommend reading a company's own website/labels to see how their marketing differentiates their various DOT brake fluid products.

When doing ANYTHING with brakes, first disconnect the battery cable, so that the brake computer doesn't detect backflow as an error and disable your ABS. I failed to do this during a pad replacement and triggered a "leak" error, requiring techstream reset.

I am sure, you are mistaken. I have done bleeding using Techstream without any issues.There is a protocol for flushing as well.

My response was intended for those who don't own a techstream device. I experienced this when I changed my front pads, having left the battery connected. When I pushed the cylinders back into the caliper the reverse flow triggered an ABS fault. I had to pay someone with a techstream to reset it.

By chance, did you happen to turn on the ignition at any time during the new pad install? Reason for asking is because when I installed all 4 new rotors & pads and 1 new wear sensor wire, the only thing I did under the hood was remove the brake reservoir cap. Install went smoothly, and I had no warning lights or codes afterward. Still no issues now after 7k miles.

You are correct. If you have the pads out and don't have something wedged in the caliper to hold the Pistons when you turn the car on to turn the steering wheel to get access to the other side of the car this will result in a code once your finished. It's best to turn the wheel to the side that you will be working on the shut the car off. One your finished that side turn the car on and rotate the wheel to the other side and then turn the car off.

I used Walmart's finest Supertech products for all of the OP's needs and, guess what, zero issues - won't be any, either. Zero ROI spending extra for fancy brands for those fluid systems.