Airbnb review are like Uber. I won't even consider staying in anything under 4.5* because people overrate them like crazy. The way the review process works most guests find it difficult to leave anything less than 4* or 5*. I see a 4* on Airbnb = 3* on Tripadvisor for a hotel.
Make sure you read exactly what the Airbnb reviews say. I find that the words are far more important than the number. Even a 4* or 5* review might mention an important criticism, and if you start seeing the same criticism even in good reviews immediately steer clear.