From my experience...the most beautiful flight attendants in the Qantas group were the link chicks!
ie. Babelink - national jet chicks
Pulse chicks - Jet Tarts/Pornstar - 717 chicks
Sunnies - Sunstate
Sunnies chicks do the walk and do the talk and do their thang during sign off and sign on. From the crew room to the car park they litterally stop traffic! The lollipop man will hold up a tug and 5 galley trucks to let a sunnies chick cross with her clear lensed CDs! It causes accidents lol
There's a couple exotic chics from Pulse --> Jetstar I can't mention any names but we used to nick name her Iman/Naomi
Link chicks are tough!
As for most beautiful...hard to say in the industry...but here's my perceptions
Aerolinias Argentinas
Gulf Air
Singapore