The finer the lime, the faster it will work, that's a fact. Think of the pellets as tiny balls. Only the outside surface of the ball that's touching soil is actually going to work to reduce your pH. The pelletized takes longer because the "ball" needs to break down into powder to take full effect. There are definitely pros and cons to each. If you're forced to use pelletized, consider plowing or discing the ground first but leave the lime on the surface so rain can hit it and help you break the pellets into powder. Just a thought.