Since you've flown UA you know that it's not a true Premium Economy product but just an Economy Plus section with extra legroom and a bit more pitch.
VS (VA is Virgin Australia) PE is a true PE so if that's available it would be worth it (bigger seat with significantly more pitch, better food / drink / service / etc.).
VS Y likely has better service (though YMMV) than UA but if pitch / legroom is important to you, UA in E+ is probably the best option if VS PE isn't in the cards.