I doubt you'll notice any difference with a 2% change in rod length. In most normally asperated engines the preference is to use a longer rod.
I think the reasoning is the long rod keeps the piston near TDC (Dwell) for a longer time than a short rod. On the intake stroke this allows the cam to open the intake valve further before the piston reaches maximum velocity. On the compression/ignition stroke it gives the fuel longer to burn with the piston near TDC creating more cylinder pressure. The longer rod would have less angle offset so it should put less side load on the cylinder walls.