I have taken quite a few genetic tests and for over 10 years have included DNA tests in talks and articles and so I am occasionally asked to recommend particular companies for tests.
I am really just a novice and am still trying to make sense of what the results tell me. But I respond “it depends on what you are trying to find out”: maternal ancestry, paternal ancestry but most seem interested in the so called ethnicity tests (autosomal). This makes sense for people with limited documentary evidence and/or mixed-ancestry but really at the moment this is the least useful for researching ancestral roots below continental level, but is great for connecting with close family.
For a recent talk recounting the motivation behind my family history research and experience researching my Barbadian ancestry I thought it would be interesting to summarise results. Some of the information has been discussed in these pages: My genes and my genes update, but I was most surprised by the results when I saw my ethnicity tests in a table.