The answer to that question would depend on the type of material one desired to present with the given language. Some languages are horrible for considering certain topics. For example, Greek has a large vocabulary of nautical terms which are highly nuanced and descriptive. Surely other languages have subjects which they are better suited to convey than Greek. There is no doubt that precision in the Greek language is possible and that perhaps more than most other languages. I don't know if I would say most exact, but among the most exact definitely.
3 things make Greek exact, first the elegance of the grammar. Greek is highly inflected which helps avoid vagueness. Subject\verb connection is easily identifyable in even the most complex sentences. Antecedents are less difficult to trace. Modifiers will agree with the words they modify, and such like.
Second, as mentioned above, the massive, and particular vocabulary is helpful for expressing thoughts clearly without confusion.
Finally, a highly defined verb system presents another "dimension" to the reader concerning time/aspect.
Hope this is helpful. Certainly there are several here who could provide a better answer and/ or correct mine. A book you may find interesting and fun for exploring this concept is "Alpha to Omega" from Humez & Humez. Why don't you stick around and learn Greek. Download one of the Grammars and give it a shot. The people here are extremely helpful