That people would recommend the f/1,4 over the f/1,8 for speed reasons is not related to the sensor size. The f/1,4 lens is simply faster than the f/1,8 (as discussed here) regardless of the size of the sensor.
However, a smaller sensor results in a greater depth of field at a given aperture. For this reason it could make sense to recommend a larger-aperture lens for a smaller sensor.
