That is a great question. It's very hard to know the difference between the woods but Pernambuco wood is much denser and make for stiffer bows.
You should look for a bow that is properly balanced, feels right from the frog to the tip. A bow with good action for staccato, spiccato and sautille. Sometimes it takes a good technique to actually know whether a bow is good in that respect.
A soft bow might loose it's form quickly whereas a good dense Pernambuco wood bow will hold it's shape longer.
The mounting is important as is the mechanism for the frog.
A Brazil wood bow can quickly loose it's shape and break much easier than other better quality wood bows and Carbon composite/fiber or fiberglass bows.
Lastly but not least, you want a bow that gives you a good sound compared to other bows.

I could probably show you easier than I can explain it in writing. LOL
You're welcome in any case.