Blades tape does make a difference to performance. In an OH6 the manual states that if blade tape is fitted ( doesnt say how much) that is equivent to an extra 70lbs on auw !
On my 500's if you polish the blades having cleaned them really well the machine will go about 5 to 6 kts faster. If you dont believe ask a glider pilot about unpolished wings or dirty wings on a glider ! was scepticle about it til I tried it !