Until joining SpanishDict a little over a month ago, my Spanish has been entirely self-taught, and one of my main "support materials" (in more ways than one) has been the NIV/NVI translation. I know that the intent of the questioner was to find the best "word for word" rather than "thought for thought" translation, but even though NIV is "thought for thought" it is very, very good. What makes it especailly good for Spanish/English study is that the translation between the two is absolutely fabulous, and the language and grammar skills you learn translate to language that is still commonly used today in both countries, which is not as true with the more antiquated versions. For Bible study I use RSV, but for reading/learning NIV, for me, is the way to go.