The “pea gravel” sound is typical of heavy rain, ie large drops. Ironically I would imagine this would be louder in the cabin at lower (approach) speeds when there’s more vertical component to it. Hail has a deeper sound and is of more concern as it does serious damage at higher speeds.
I’d also add that snow is a more difficult diversion call, especially at single runway airports where they have to close for ploughing (plowing to the yanks). Fortunately the Canadians and Scandi airports are experts at providing good info to approaching flights for decision making. The Brits not so much. Landing in falling snow on a recently ploughed runway isn’t a big deal unless there’s a crosswind, which is disorientating and can affect directional control if it gets slippery.