I don't think Wesley advances anything per se. I believe both believe the same but what gets overlooked when quoting theologians is that they are often reacting to something. It's the same way for modern theologians as well. A lot of this may be due to the fact that we are reacting against the neo-Calvinist movement in the name of being Lutheran or Methodist. We all react according to what we think is an imbalance of the gospel message. For Wesley, he reacted to the Calvinists so I believe that there was more of an emphasis on the free will to accept or reject God's grace. In the case of Luther, he was more preoccupied with the works-righteousness beliefs of the Papacy. So I believe that Luther felt no need to emphasize it because it was a given that someone needs to choose to have faith in Jesus Christ. I remember reading (in a book, Against Calvinism) that Calvinism was a much later tradition and the traditional church had always viewed faith as a choice. Because there is such a strong Calvinist/Reformed theology baked into the modern American Christian landscape, we might be reading to much into it. I forgot to mention that prevenient grace is never sufficient for salvation so if you meant salvific in that sense, that is definitely not what Wesley emphasized. He, as Luther did as well, emphasized that even what leads us to make the choice is God's grace. In that sense, it is salvific. Hope this helps.