Interesting, the dentists I have asked (4) all said it doesn't matter (Spain and Germany, maybe it's relevant) at all and it's up to personal preference.
Also: floss and mouthwash. Like floss is really important…
Why can't we in the US just have nice cheap things. Why is everything an electronic life-hack with a fun take on how to be eco-concious, that involves buying something I don't already own?
For what it's worth, the toothbrush was also not the cheapest I could find (that would have been Lidl or somesuch), and was made in France, so maybe that makes a difference.
Also, dentists recommend X-rays A LOT, too.
You can find electron microscope scans of fresh toothbrushes and worn ones in this[0] Applied Science YouTube video.