It's usually good enough, however I've found a number of lower quality USB enclosures that handle things better when setting it as high as 32MB so that as much data is in buffer as possible for them at all times. any higher and I've not seen any speed difference but below 16MB and they'll run at nearly half speed for some reason.
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Linux's disk caching is good enough that I haven't been able to observe a difference when I change bs= on Linux. But it certainly won't hurt.
It's usually good enough, however I've found a number of lower quality USB enclosures that handle things better when setting it as high as 32MB so that as much data is in buffer as possible for them at all times. any higher and I've not seen any speed difference but below 16MB and they'll run at nearly half speed for some reason.