finasteride reduces DHT at around 70% in the blood and is said to directly effect such DHT at the scalp level.
SP has been shown in studies to reduce DHT in the blood by 30% yet not proven to effect the scalp although it may. SP works better with a few other ingredients like Pumpkin Seed, etc.
finasteride in the generic form is much cheaper IMO. I get 30 5mg pills that I cut into quarters the best I can. I get mine from Target bypassing my insurance because they are too expensive. So I pay directly $9 for 30 pills which comes to a 4 month supply. Or $27 for a year of finasteride. Can't say that I have regrown anything after 18 months especially in the front (receeding) but I'm just trying to hold on to what I have until a miracle is found.