Hey Flamenca Blanca,
You're going to have to change your handle to 'flamenca negra' with such an interest in rosewood!
There are a lot of great comments here on the two rosewoods.
It's very difficult to generalize about the physical difference in the properties of the Indian versus Brazilian. I build almost exclusively with Indian rosewood, but use Brazilian, and increasingly more with Cambodian rosewood and other Dalbergia's.
The properties of the wood has less to do with what species of rosewood it is and more to do with the growing conditions encountered by each rosewood tree.
There is old growth Indian rosewood which is hard and heavy, and there is plantation rosewood, used to shade coffee trees. The plantation rosewood has wider grain, and tends to be a lot lighter in weight that the old growth stuff.
I have been told that Brazilian rosewood is now being grown in plantations in Brazil, but that the trees won't be ready to harvest for a long time. These trees grow fast and therefore won't have the higher density of the old growth wood.
Is this plantation wood bad for making guitars? Certainly not. If it's straight grained, well quartered, and seasoned properly, it will be fine for guitars.
A good luthier will take the lighter weight of the plantation grown wood into account when voicing the guitar. He may decide to make the back thicker, or laminate the sides.
But many luthiers are still 'stalking the wild asparagus', and want the old growth wood. Some argue that it is more reflective and is therefore better for concert instruments, where projection and clarity are required.
We've started to see African Blackwood, Ebony, Honduran, and Cambodian rosewoods employed for backs and sides on concert guitars to achieve this end.
I think that the jury is still out on whether or not these woods, often being extremely hard and heavy, make better quality concert guitars.
I heard Paco Pena play his blanca in the Q.E. theatre in Vancouver some years ago. He filled the hall with that small cypress box....
At the end of the day, I still believe that the skill of the luthier, and the design of the guitar is more important than the type of rosewood used.