Very true,
Speaking of my own personal knowledge i have a friend that flies for a Portuguese Airline, he started flying has Cabin Crew then he got a chance and went on to fly the B737 and now he is flying the A310 ( Same Airline ).
The advantages, well you get to know people make contacts, you are already working for the airline which makes it easier interview wise, and market knowledge. Surely a plus.
Best of luck
Regards,
Cpt Efis