About Proscar and Propecia, it does not matter between the two, both of them contain the exact same medication, which is Finasteride. Proscar is 5 mg per tablet while Propecia is 1 mg per tablet. Buy Proscar if you want to save money, you can take the 5 mg tablets of Finasteride, cut them into fourths, and take 1.25 mg daily, it's a lot cheaper using this method than buying the standard 1 mg tablets.
I currently do not know much about RU58841 and cannot give you any recommendations with that treatment, especially that of this post I haven't had any experience with it.