I have seasonality in my data. Which method is best to use?

CB Predictor 1.0 has 4 seasonal time-series methods: Seasonal Additive, Seasonal Multiplicative, Holt-Winter's Additive, and Holt-Winter's Multiplicative. Seasonal Additive and Seasonal Multiplicative were designed to forecast data with seasonality, but no trend. The Holt-Winter's methods were designed to forecast data with seasonality and trend. 

So, if you think your data is seasonal, but has no trend, you can try Seasonal Additive and Seasonal Multiplicative. If you think your data has both seasonality and trend, try the Holt-Winter's methods. 

However, the best alternative is to select all the methods in the Method Gallery (unless the length of time to run the forecast is very long), to make sure that you don't rule out a method that works best for your data.