Actually, it is that hard. I needed some CR32032 batteries, and looked on Amazon. Guess what? There's a ton of sellers, claiming to sell from a ton of vendors. I'll guess that many of them will sell me a battery with the right physical and electrical form factor, but....
Which brands last longer?
Which sellers are selling official brands, and which are selling indistinguishable knockoffs?
Are the knockoffs actually worse?
Is something that looks more official and appears more reputable actually selling something better? Or am I paying for reputation and not actual quality?
How valid are the reviews? Are they astroturf? Does it matter? How can someone tell a good battery from a bad one, anyway, right after getting it. Are the just giving 5 stars because the batteries came quickly in nice packaging?
I think these are all reasonable questions, but I don't have an answer to any of them. I'm hoping that someone has done a real comparison, and can provide some kind of solid data.