Assuming both your finasteride and dutasteride are genuine, (in my case, I'm 99.999% sure both of mine are genuine), I'm also very puzzled why finasteride seems to work better. I've made the switch 2 years ago, I've lost quite a lot of hair in the frontal area, only recently started to grow back. If that was a shed, that was a very nasty shed!
How could that be, dutasteride inhibits type-2 better than finasteride, in addition to inhibiting type-1 also!
It also doesn't make sense to say some genes respond to finasteride better than dutasteride, while others respond to dutasteride better, because both finasteride and dutasteride are designed to work with standard type-1 and type-2 5AR enzymes. If your genes are slightly mutated, both finasteride and dutasteride should not work.
The only explain I could come up is that, dutasteride raises Testosterone more, and testosterone promotes facial oils, and facial oils somehow interfere with hair growth in the frontal area.