Pernambuco and Brazilian Rosewood necks both sound great. I'd say Brazillian Rosewood is a bit darker and generates a more of a scooped tone. The main difference is the feel (raw rosewood vs. a finished neck).
Interesting. My situation is opposite. I really like the Brazilian neck, but would like to give the Perny a try.
I do have acoustics with braz and Perny (different guitars) and from them would go along with braz being a bit darker. Both are very well balanced and have excellent sustain. I love both guitars, but the harmonics from the pernambuco can take your breath away - which is why I'm keen to see how it translates to the neck of an electric.