This is my first time running Mk and Gw so I'm opting for the lower doses. I do it this way so when I see results with 5mg/day then I can compare them to my results when running @10mg/day in a future cycle...If I see double the results than I will know it's better to run @10, but if I only see a 10% increase in results for double the dose I will know to run @5mg and simply extend the length of the cycle. I don't see the need to start at the high end when you could be wasting a lot of money.
This is how I run supplements because I have confidence in my diet and training and know I can make slow improvements without all these supplements, although they are fun as hell to run and see your body reacting and performing on another level. Sometimes I think people jump to higher doses to cover up weaknesses in training, diet, commitment, etc...that's just how I look at it and why I try to start at the lower end.