Definitely granular form. Disperse below to immediately control ones at the bottom, while the surface will get the payload as the chemical floats to the top.
However, my suggestion is a half-half approach. The granular version has a heavy weight formulation to keep the chemical at the bottom. Only about 15% will float to the top. The liquid utilized an oil base emulsifier that keep the chemical at the surface, but will eventually sink, which is only ~5%. So, half bottom, half top version.
