οὐκοῦν τὸ μὲν ‘συμφέρον’ ἤδη που κἂν σὺ εὕροις ἐκ τῶν πρότερον ἐπισκοπῶν:
Socrates
You might by this time be able to find the meaning of συμφέροντα by yourself in the light of the previous explanations,
Of course, even you would be able already to find out the meaning of ‘useful’ considering the foregoing.
Which translation is more accurate?
and again 417c: ταύτῃ μοι δοκεῖ ἐπιφημίσαι τὸ ἀγαθὸν λυσιτελοῦν:
It is in this sense, I think, that the good is dubbed λυσιτελοῦν,
It is in this way that I think it appropriate to call the good ‘expedient’.
The translations quoted first are from Persues.
Both versions look ok to me. It depends what you want from a translation, and what you mean by “accurate”—a question worthy of the Cratylus itself!