The 5 seconds of Google research I did says that both ways are considered correct. From here:
“Vice” as one syllable may be considered correct, but it shouldn’t be.
The final syllable in “vice” tends to be very short, and often is ALMOST swallowed going into the v of “versa,” but that’s not the same as making “vice” just one syllable, which is a crime against nature, humanity, and all things good.
What are those kids doing on my lawn?
Do you pronouce it “VEE-kay” or do you just half-ass the latin?
It’s one syllable, like the opposite of virtue.