Most everything is going to be standardized at 15%, which is fine. In terms of brands, I honestly have not noticed much difference in them, but do like Solaray brand in general. I've always liked it for the feeling of well being that it provides.
With that all being said, I've yet to find anything that touches Endosurge. I ran it for over a year (cycled every 8 weeks) and loved it. I just started taking it again and remember how good it makes me feel. It's standardized to 75% l-dopa for 83mg and 25% l-dopa for 100mg. To me, I notice that concentration more than 300-400mg standardized to 15%.