You mean analogRead(), not analogWrite()
I think it depends on the range of temperature you are looking at - the smaller the range the simpler
the curve needed to fit to the device's response over that range.
For a very small range a linear approximation might be enough, somewhat larger you could try a
quadratic curve or cubic.
For a large range of temperature the Steinhart–Hart equation will be best simply because it has the right
form and fewer parameters are needed to get a good fit - otherwise a polynomial or rational function
approximation with more parameters would be needed.