The write speed supported by the media is unrelated to what it can be used for. Assuming the write process is good enough, it is also unrelated to the attainable read speeds. I have old 2x and 4x CD-Rs that were recorded way back in the proverbial middle ages, and they read back a lot faster than that on modern, fast readers (though, due to media degredation, usually not at full speed).
So no, buying media that supports a higher write speed presents no direct benefit if you can live with simply the write taking longer. But since Blu-ray (just like CDs and DVDs) is a WORM (Write Once, Read Many) type media, write speeds should not be much of a concern unless you are writing a large number of disks. The media can be used for the same purposes, regardless of its maximum rated write speed; like with CDs and DVDs, the read speed is limited primarily by the device used for reading the disks, and secondarily by the quality of the recording (which is impacted by things like the specific dye composition, recording speed used, media deterioration, and more).
Using media rated for a higher maximum write speed, and actually recording the media at that higher speed, means that the write process will finish sooner than if you used media that required writing at a slower speed. Media rated for a higher maximum write speed within the same quality range is usually more expensive at any given time; hence, the faster write speed comes at a direct monetary cost. The issue here is whether the time savings when recording the media offsets the additional expense of the "faster" media. That is a judgement you will have to make for yourself; we cannot make it for you, and any question here on the outcome of such a judgement would highly likely be closed as "primarily opinion-based".
Higher rated write speeds may be related to higher quality media, but that is not guaranteed. If you want higher quality media, then buy from reputable vendors with solid reputations rather than blindly looking for the highest rated write speed. Since product recommendations are off topic here, I will refrain from guessing which vendors that might be.