I am going to use Sentinel-2 images for crop type classification, and I am new to remote sensing. I want to know if there is an added value when using both L2A and L1C images. From what I understand, I think L2A is better and works just fine when using it on its own since it has the advantage of being atmospherically corrected, but I would like to get experts' knowledge on this.
It is always preferable to use bottom of atmosphere reflectance (BOA) products (e.g. L2A) instead of top of atmosphere (TOA) reflectance products (e.g. L1C). For example, the image below shows a L1C scene on the left with significant scattering and a L2A scene on the right that has been corrected to BOA reflectance. Using BOA reflectance products will allow you to integrate multiple scenes from different time periods and accurately produce vegetation indices.