Well if you look at the difference that makes for even ranked teams. I think this section looks nice.
normal version (1 for win, 0 for loss):
k(1 - .5) = .5k
k(0 - .5) = -.5k
Pts version (50 - 0 score)
k((50 / (50 + 0)) - .5) = .5k
k((0 / (50 + 0)) - .5) = -.5k
Pts version (50-10 score)
k((50 / (50 + 10)) - .5) = .33k
k((10 / (50 + 10)) - .5) = -.33k
Pts version (50-25 score)
k((50 / (50 + 25)) - .5) = .16k
k((25 / (50 + 25)) - .5) = -.16k
Pts version (50-45 score)
k((50 / (50 + 45)) - .5) = .02k
k((45 / (50 + 45)) - .5) = -.02k
And now for teams that are unevenly ranked (.6 vs .4 chance to win). The last case is interesting, as the team that wins still loses points in the match, as they are expected to have a bigger point differential. I'm not a fan of this idea at all.
normal version (1 for win, 0 for loss):
k(1 - .6) = .4k
k(0 - .4) = -.4k
Pts version (50 - 0 score)
k((50 / (50 + 0)) - .6) = .4k
k((0 / (50 + 0)) - .4) = -.4k
Pts version (50-10 score)
k((50 / (50 + 10)) - .6) = .23k
k((10 / (50 + 10)) - .4) = -.23k
Pts version (50-25 score)
k((50 / (50 + 25)) - .6) = .06k
k((25 / (50 + 25)) - .4) = -.06k
Pts version (50-45 score)
k((50 / (50 + 45)) - .6) = -.07k
k((45 / (50 + 45)) - .4) = .07k
It gets much worse in a case where a team is farther ranked apart. For example, a team with a score of 1800 playing a team with 1200. The 1800 team has a 96% chance to win. Now in this case, even when a team wins with a 50 - 10 score, they still lose points. And a fairly substantial amount. The 45 - 50 game they lose almost half a k value, which is kinda crazy. In a normal ELO system, this is accounting for a tie scenario where a team is expected to win, not tie. But in pb, 50-0 is the same as 50-49, so it really doesn't work out.
normal version (1 for win, 0 for loss):
k(1 - .96) = .04k
k(0 - .04) = -.04k
Pts version (50 - 0 score)
k((50 / (50 + 0)) - .96) = .04k
k((0 / (50 + 0)) - .04) = -.04k
Pts version (50-10 score)
k((50 / (50 + 10)) - .96) = -.13k
k((10 / (50 + 10)) - .04) = .13k
Pts version (50-25 score)
k((50 / (50 + 25)) - .96) = -.29k
k((25 / (50 + 25)) - .04) = .29k
Pts version (50-45 score)
k((50 / (50 + 45)) - .96) = -.43k
k((45 / (50 + 45)) - .04) = .43k