This hinges around what is meant by 'hard to land'. Some types have less margin for deviation from the correct technique than others; perhaps that could be one definition. Some require greater control activity in aspects such as directional control after touchdown; perhaps such increases in workload could be another. Some require atypical techniques such as raising the flaps before lowering the tail in a crosswind; that increase in workload could, perhaps, also be considered as 'harder to land'. Generic phrases such as this need careful definition if they are to be used in a meaningful manner. But on a gusty day with a strong crosswind and a short, wet runway there are certainly some types that I prefer flying more than others!