Genoas have the most affect on boatspeed of any upwind sail on a boat since there is no mast in front of it disturbing wind flow. If only one sail is in the budget, start by replacing the genoa. Racing sailors have different genoas for different wind speeds. The most powerful sails are called No. 1’s and as sails get smaller and/or less powerful, their designation change to No. 2, No. 3, No. 4 down to No. 5. Cruising sailors, usually sail with smaller inventories since changing sails is difficult for smaller crews. For simplicity, cruisers compromise performance for the ease of using roller furling genoas.