Both of those people would be equally unacceptable as a professional translator. It&#x27;s true that #2 would be better if those were your only two options, but that&#x27;s an unrealistic limitation.<p>A guy who is 99% fluent in source and 100% fluent in target will generally produce a flawless translation--if he happens across a word or idiom in the source that he doesn&#x27;t quite understand, it will stand out to him, and he will pause to research it before continuing.<p>A guy who is 100% fluent in source and 99% fluent in target will produce a perfectly clear but very slightly stilted translation, because he&#x27;s not aware of the few mistakes that he makes.<p>If you&#x27;re translating a commercial product and you have my two guys to choose between, you would want #1.