I have a variety of results across the companies (with many significant changes of regions and % in updates over the years). This provides an example of why it is an "estimate" and should not be used to change your identity. (e.g. start wearing a Kilt instead of Lederhosen) I have also noticed differences between a directly purchased kit and an upload from another company.
Personally, I find Ancestry currently has the "most accurate" results compared to what I have found in research especially when using their Communities and Side View.
Expected Ethnicity Mix (Family Knowledge & Research)
Czech: 25%
English: 25%
Swedish: 25%
Irish: 25%
Ancestry DNA
Sweden & Denmark: 35%
England & Northwestern Europe: 26%
Ireland: 20%
Eastern Europe & Russia 11%
Scotland: 6%
Baltics: 2%
23andMe
British & Irish: 50.8%
Scandinavian: 22.4%
Finnish: 0.6%
Eastern European: 14.7%
Greek & Balkan: 2.1%
Broadly European: 0.7%
North African: 0.1%
Unassigned: 0.2%
My Heritage DNA Kit (and 23andMe Upload to MyHeritage)
Scandinavian: 75.7% (76.8%)
Irish, Scottish and Welsh: 15.3% (12.9%)
East European: 8.1% (3.8%)
Italian: 0% (3.5%)
North and West Europe: 0% (3.0%)
Baltic 0.9% (0%)
FTDNA
England, Wales, and Scotland 35%
Central Europe: 22%
Scandinavia: 18%
Ireland: 10%
Baltic: 7%
East Slavic: 6%
Basque: 3%
Italian Peninsula: <1%