I think what you have represented between the GNT and the NRSV are two polar ends of biblical literacy.
If I am not mistaken, the GNT intends to appeal to persons whose biblical literacy isn't quite up to par. It tends to be quite paraphrastic, conveying preinterpreted concepts with modern English. I think the idea was to get people to say, "Oh, so that's what Jesus meant when he said...." But, did He really mean that specific interpretation only? Not often. However, as I think this is sort of a "third-world" or ESL (English as second language) Bible, it does its job in getting people to at least pick up a Bible and read it. I've only see one biblical scholar recommend it as a choice text for serious study.
The NRSV, being the base text of the NOAB, is the choice text for serious biblical study. Some contend that it is the most accurate translation we have available, which is why I think most serious biblical scholars prefer it. The biggest criticism I have ever seen in terms of this Bible is in relation to its gender inclusive language. Most people outside academia consider this one factor to be an unfortunate yet considerable blemish when choosing a faithful translation. However, I have seen some Orthodox blogs which praise the accuracy of the NRSV translation even in light of the gender inclusive language.
The NOAB is great for in-depth scholarly study, but I've rarely found anything in there that I couldn't live without knowing. I personally have so little time to spend reading the actual text of the Bible that I really am not concerned with any of the major "criticisms" of the text (historical, form, source, etc.).
As far as the "perfect" Bible, I think such a search will end in vain. Such a desire, I think, is due to our highly consumerist, perfectionist society, where we have so many options to choose from, each with varying degrees of "bells and whistles." Going back to the GNT - if I lived in the third world and someone gave that Bible to me, I would treasure it like the pearl of great price! Ungrateful consumers that we Westerners are, we're afraid to be satisfied with what we have. I speak largely for myself, though.