These days I have the luxury of online genealogical resources, and the ability of searching online data bases. To cut a long story short, I have accumulated a family history that includes the names of 279 recorded, direct ancestors, 277, of which lived in South East England, particularly in the East Anglian County of Norfolk (the other two were a Swiss 3 x great grandparent and his named father).
At Generation 6 (3 x great grandparent), I can say that on paper, I am 97% South East English (including 75% East Anglian), and 3% Swiss. In other words, pretty much of local East Anglian ancestry. Here is a map showing my recorded ancestors - blue via my father (minus the few in Switzerland), red via my mother:
Okay, I will still have some mistakes in my genealogical research, particularly on more distant lines, where records start to be come more scarce and have less survival. There would also be some NPEs (non parental events). However, if I compare my pedigree with DNA matches / cousins that share common ancestors both in segments and on paper trails, I get this (shaded areas verified with DNA matches to paper trails):
That is my background. The results? Remember, Generation 6:
Well before phasing, 23andme gave me:
100% European: 94% NW European. 3% Southern European. 3% Broadly European. Broken down to:
32% British & Irish
27% French & German
29% Broadly NW European
2% Broadly Southern European (including 0.5% Iberian)
After phasing with a surviving parent, it adjusted to:
100% European: 96% NW European. 2% Southern European. 2% Broadly European.
38% British & Irish (23% from father, 15% from mother)
24% French & German (13% from father, 11% from mother)
0.8% Scandinavian (from mother alone)
34% Broadly NW European (22% from father, 12% from mother)
2% Broadly Southern European (1% from father, 1% from mother)
Not very impressive is it?
AncestryDNA gave me:
Still way off, but a lot closer and more precise than 23andme. They also assigned me both to the Southern England Genetic Community, and to the East Anglia & Essex Genetic Community, perfectly correct.
Therefore in summary - I've come to the conclusion that NO current autosomal DNA test for ancestry is capable of accurately predicting your ancestry below a very large region, such as NW Europe - unless your ancestors belong to a particularly well defined population that avoided medieval admixture. They are all inaccurate. More important to me now is that they have fat databases of testers, with a system of searching them alongside family trees, ancestor locations and surnames. However, side by side - for my results, and weighed simply against recorded family history, I have to pronounce AncestryDNA/.com to be more accurate than 23andme.