Dutasteride blocks two types of enzymes, and finasteride only one of them. Type 2 is the one which is responsible for hairloss, and they both take care of that, but dutasteride is more potent. Dutasteride is not approved as hairloss treatment, and you've only been 8 months on finasteride, so I would stick with that.
And by the way, if you decide to switch, I would use proscar for atleast 3 months first. 5 mg is a little more effective than 1 mg considering hairloss, but you have a greater chance of experiencing side effects. Even 5 mg a day can't compete with dutasteride. Just imagine the side effects, if you should get hit.