I suggest you search some of Bryan's old posts. He has plenty of information on this subject and studies linked it to. I can't find the studies right now as I am not home. Don't listen to K9gatton he is giving you the wrong information and most people on these forums have no idea what the actual difference in Finasteride and Dutasteride is.
There's no difference in liquid finasteride... and I have no idea where he comes up with this idea. Finasteride hits a plateu around 5mg regardless of form.
Read this study
http://www.bernsteinmedical.com/resources/hair-restoration-papers/dutasteride-vs-finasteride/ although not from ncbi, it shows you the different numbers. However, serum DHT is not important, the main reason dutasteride is better than finasteride at supressing serum DHT is due to the fact it also inhibits type
Type I 5 alpha reductase isonenzyme, but this has no correlation with hair loss. You can see that in the study developed by Merck where they have a specific substance that inhibits only type I and they found no correlation to hair loss.
However Type II is important, and the Pseudohermaphrodites who lack this specific isoenzyme has no hair loss; hence you need to focus on the amount of type 2 dht that finasteride and dutasteride supresses.