The OED is a historical dictionary, which means it shows the meanings of words as they developed over time. People use it as a standard, but it does not set out to be one, and the editors of the OED discourage people from deciding whether or not to use a word based solely on its inclusion in the OED.
The New Oxford American Dictionary is not a historical dictionary, but a dictionary of current English, and is much smaller than the OED in the number of terms covered. (If you have a Mac, you already have this dictionary, because it's the dictionary used by the Dictionary Widget in the dashboard.)
If you are looking for a dictionary that set itself up as a standard, especially for scientific and technical vocabulary of the day you might look at the Century Dictionary(commentary at link). It has not been updated for about a hundred years, though.
The bigger question is: what do you want a standard for?
To tell you whether or not something is a word? No dictionary will tell you that, only usage.
Etymology? The OED is among the best for etymology, although there are other sites that have better ones for particular words (and despite the Century's age, its etymologies are on a par with the OED).
Advice on correct or accepted usage? You'd be better off with the Dictionary of Modern American Usage.
An impressive book to put on a stand? True dictionary aficionados like Merriam Webster's Second International (rather than the third), as a prestige thing. (Or again, a copy of the Century, although that's ten volumes.)
