The time to upgrade the BlackBook was several years ago. I don’t think I’d bother upgrading a BlackBook in 2017, as it’s far too limited, with only legacy OS support and poor software support.
The 2010 white MacBook is definitely worth upgrading though. That machine would run extremely well with 8 GB RAM, SSD, and 10.13 High Sierra. That model can take 16 GB I believe but that’s overkill.
Basically I think the MacBooks worth upgrading are the Unibody models, beginning with the MacBook5,1 aluminum model from 2008.
I haven’t used the Samsung 850 EVO in that MacBook7,1 but have an 840 EVO in a MacBookPro5,5 and it works well.