Walz came across as nice, good guy but a bit naive. Vance was outright Macchhiavellian, eloquent but ruthless, completely dishonest and calculative.
You could still tell when he was lying by contrast. When it came to the only topic where Trump could score somewhat ("bringing manufacturing back to the US") you could feel that Vance was less calculative, showed less controlled tension because he knew a that for once he had a real talking point (the only one) where he didn't need to lie.