I have tested with Ancestry, and I think they're the best. Ancestry's analysis was very accurate for me- much better than the analysis on FamilyTree DNA. I downloaded my Ancestry .com DNA results to my computer and then uploaded my DNA to the free website Gedmatch that has several analysis tools not available on Ancestry including exact chromosome matches with other members and several ethnicity tools. I recommend Gedmatch.
I also uploaded to FamilyTree DNA for a small fee but their ethnic breakdown was much too general and not very accurate so I don't recommend them plus I have a hard time navigating their website.
I like Ancestry's website which was invaluable for me to find out my ancestry due to their DNA matches with cousins who have trees you can look at. I knew almost nothing about my ancestry 2 years ago, but I now have a tree on Ancestry with over 700 ancestors I have confirmed with extensive research. Just by taking their test, you can set up several trees without even paying for membership. I have only paid for a couple months membership. Soon after I tested and they did my DNA matching, I heard from 2nd, 3rd, 4th cousins I had never met but who knew more about my great grandparents than I knew and were able to help me tremendously. The accuracy of the degree of relationship of DNA match cousins is very good.
For me, Ancestry was much more specific and accurate than FamilyTree DNA but for certain areas Ancestry .com cannot distinguish. For example, Italy/Greece is combined and Italians or Greeks will get a result showing significant West Asian/Middle East/Caucasus ancestry even though they have no Middle Eastern ancestors for at least 600 years+.
I have 30% British ancestry and a little Irish, and a little Scandinavian which Ancestry .com accurately detected while FamilyTree DNA didn't show any British Isles ancestry for me at all. And Ancestry correctly found zero Iberian (Spanish/Portuguese) for me while FamilyTree DNA mistakenly lumped Iberian together with my predominantly Southern Mediterranean ancestry.
My only serious caution in using Ancestry is that a lot of people there have erroneous information in their trees, so you have to do a lot of independent research and use a variety of alternative online sources to insure accuracy rather than assuming other people have posted correct information.