I have heard both models but in totally different systems, different rooms, different times. It's tough to draw solid conclusions from that type of listening, but I think you are generally right with your research about polite versus lively.
I would think the Legacy set would be superior for more modern records. If you play a lot of rock, pop, girl with guitar, and similar music, they would be more dynamic and impactful, also have more snap. But for jazz I think they would be inferior to your ProAc set. Especially when factoring in your Unison amp which is probably an ideal match for the ProAc and not really that great for the Legacy.