In my case, I use Blackstone for all my UOAs except for the engine oil on my track car. For that, I use SPEEDiagnostix for a few reasons: (1) from mailing to receiving the report, it's consistently 7 days, (2) they understand my use case much better and can give more detailed recommendations, (3) FTIR for oxidation oil analysis vs TBN, (4) RDE instead of ICP for the elemental analysis. Overall, I've been happy with them for this particular use case, for other lower requirement use cases I still use Blackstone.