SureAI

In terms of content and playthrough hours, how those games compare?

Well in terms of playthrough time, that is always a bit hard to calculate
In Nehrim you could sink more than 100 hours, in Enderal it is at least the same.
The time to complete the main quest is different though: Lord Dagon wrote 2 months ago that for a mainquest run in Nehrim he (as developer) needed 20 hours; in Enderal at least 30, so 50% more.

In terms of content Enderal seems to be better aswell: The amount of sidequests is much higher (though still nowhere near the amount of Bethesda's )
The other factors like size of the world map, amount of dungeons and other activities in comparison to Nehrim is hard to determine - but the new housing system alone will take people (who want that) hours for furnishing their houses like they want them to be