I have used both AncestryDNA and FamilyTreeDNA. I have worked with FamilyTreeDNA for much longer, so I may be biased toward using their interface. Both have their pros and cons.
- more testers in the database,
- automatic tree hints and tree circles help find common ancestors based on your Ancestry tree (this can save a lot of time and effort for adoption-like searches),
- more testers with early American roots
- no chromosome browser,
- messages to matches go through their message service (I have experienced a very low reply rate with notes to even “2nd cousin” level matches),
- testers less knowledgeable about what their DNA test results mean,
- in-common-with matches not shown beyond the “4th cousin” level,
- no X-DNA information
- chromosome browser,
- get your matches’ email addresses,
- more international testers,
- many testers are more serious genealogists,
- in presentations and papers well-known genealogists like Thomas Jones and Elizabeth Shown Mills have shown their DNA results through this company,
- surname lists shown next to the individual matches help narrow down where common match may be,
- shows X-DNA matches (though be wary of small matches),
- ability to sort matches in common with or not in common with individuals
- fewer testers in the database,
- it seems not as many people post their trees at the site compared to the number of results with linked trees on Ancestry, though you have their email to ask for a tree
- need to go through the results yourself vs. Ancestry’s hints for common matches
Some of the Ancestry problems can be worked around by bringing your results to gedmatch, but good luck getting your matches on Ancestry to move their results there.
Also, FamilyTreeDNA has had a feature to import results from Ancestry and 23andMe. Unfortunately the ability to transfer from Ancestry has been halted and been under construction for what feels like a few months now. If and when this comes up again, it could make sense to test at Ancesty and transfer to FamilyTreeDNA.
Another big tester is 23andMe, but they focus more on the inherited trait medical side and only recently came out with a family-only test at a similar price point to the others. MyHeritage recently launched their own DNA test.
I have generally tested at FamilyTreeDNA, except with family where I want to focus on really early American roots I have tested at Ancestry, and for the adoption-like search in my tree we tested at both. (23andMe is on the to-do list for that branch also.) Whatever testing service you choose, don’t forget to bring your results over to gedmatch.