It does matter what strength you use. RetinA comes in 3 strengths for a reason. You start with the lowest strength and work your way up. Many patients never get to the highest strength. Start with the 0.025 % using it every 2 to 3 days. Be sure to consult with your Board Certified Plastic Surgeon or Dermatologist regarding your treatment.
Yes, it matters what strength you use, as well as what brand and whether you use a cream or a gel compound. See a dermatologist for a recommendation and appropriate prescription. Remember that Retin-A can cause severe irritation, especially in the beginning, so using a higher dosage or using it more than prescribed, will not get you better results!