The ESV seems to be everywhere on the Logos site, including reftagger, many (most?) training videos, etc. If you do some casual research you will come to the same conclusion as me.
However, the ESV is neither the top grossing translation or the top selling translation. It never has been the most widely used translation by Christians in general. As of June, the ESV is still stuck at number 4 and five for unit sales and dollar sales. (Ref: http://cbanews.org/wp-content/uploads/sites/3/2014/05/BiblesTranslations201406.pdf)
Logos does not claim to take sides with any denomination, but markets to all kinds of Christians. Here are some points I would like to make:
1. They are a business, and they should be more neutral in regards to the issue of Bible translations. They should choose a default translation based on what is most commonly purchased/used by Christians.
2. In addition, they should choose a default version that was translated by a team from all different theological perspectives, not only, for example, the Reformed perspective. (I am not saying anything against the Reformed perspective, that is not my concern here). If one examines the translation and review team of the ESV, one can see clearly that nearly all of the involved come from Reformed institutions or ones closely associated with the Reformed perspective.
3. Many contemporary and scholarly commentaries are based on the NIV, for better or for worse. Very few that I know of are based on the ESV.
Overall, my opinion is that Logos should market to the whole church. Choosing the ESV as the default translation for the Logos website and training, etc., gives the wrong impression. (That they are promoting the Reformed faith). I am not saying that the impression is right.
All translations have weaknesses, including the NIV and the ESV. Why not make the NIV the default translation of Logos, then, starting with Logos 6?
As the market widens, just go with the numbers.
NOTE CAREFULLY: This post is NOT about doctrine or theology. It's about Logos not giving a false impression, and going with the common sense reality that the ESV is not the Bible that most Christians use.
So please do not start a theological discussion.
NOTE ALSO: I am neutral when it comes to what translation is best. They all have good and bad points. I can and will use all of them.
Since that is true, in general I use the NIV for most things, due to the points mentioned above.