Those things are fun but mad inaccurate. Every once in a while they update their genetic pools and it completely changes your results.
From what I've seen, when looking at the ancestry percentages at the continental level, they don't change much. Like if it says you've got 80% sub Saharan African ancestry and 20% European, it's not going to vary much if you do it at 23andme or ancestry, or if either of them update their estimates. Now with the more fine-grained breakdowns, like Irish vs English or German, or Senegalese vs Nigerian, there can be more variation from one company to another, or significant changes with updates. And especially with new world black people, who are centuries old mixtures of different African ethnic groups, I wouldn't expect precision in any of the intra African breakdowns.
From what I've seen, at the continental/racial level, 23andme at least, is pretty damn accurate and aligns with people's known genealogy.