Still a sloppy and lazy argument to use WS and WS only. I'd say all advanced stats, while generally useful and providing good insight, are incomplete and less useful when used by themselves in an argument without context, additional statistics, and other facts or factors.
Let's use this WS stat in another player comparison. Here are the top 5 WS seasons of four players, so it's not just each player's top 1 or 2 seasons:
Gary Payton: 13.9, 12.9, 12.6, 12.5, 11.7
Jason Kidd: 11.3, 10.1, 9.6, 9.3, 8.9
Steve Nash: 12.6, 12.4, 11.6, 10.9, 10.5
Chauncey Billups: 15.5, 13.5, 12.1, 11.4, 11.3
Now, based on your win shares argument, not only was Billups at the same level of GP and Kidd and Nash, but he had clearly been the better player than Kidd and Nash in his best seasons. And at peak, he was better than all three at each of their respective peaks. His top 4 win share seasons trump any season Kidd ever put up. Better at his peak than peak Payton and peak Kidd? Maybe you do believe he was a better player. But even as a Pistons fan, I don't think he was. Billups WS output was a big product of being on a winning team with other very good complementary players. Win shares obviously relies at least on a base level to team success as well. Billups was ball dominant on offense and his DWS was greatly aided by playing in front of Wallace/Wallace and having a strong wing defender in Prince to always take the toughest perimeter defensive assignment. I still don't know why Billups ever got NBA defensive honors. His high defensive win shares in those years do not accurately reflect his defense.
How about this comparison:
Tim Duncan's best two WS seasons: 17.8, 16.5
Karl Malone's best two WS seasons: 16.7, 16.4
Now you can see why these two based on two of their best two WS seasons can be considered among the all time greats. But also consider this. Karl Malone also put up another 7 seasons with at least a 15.0 WS. After his top two WS seasons, Tim Duncan did not put up another season with better than a 13.2 WS. Who would you say had the better overall career... based only on the WS stat? 99.9% of the basketball world acknowledges Tim Duncan as the best PF in NBA history. A WS argument, although close, would favor Karl Malone.
Or look at last season and over the careers of Tony Parker and Chris Paul. Last season, an interesting debate arose whether Tony Parker had surpassed Chris Paul as the better PG. Well based on a WS argument, it wasn't a debate at all. Last season and over the course of each of their careers, Tony Parker has never been at the same level as CP3... based on a win shares argument. Win shares don't even allow the debate to be close. I think most agree that it was at least a debate.
You see what I'm saying about using one advanced stat and one advanced stat only to make an argument? It's incomplete. It's sloppy. It's lazy. Give more context, more explanation, more additional statistical evidence. Win shares in addition to other advanced stats, basic standard stats, team dynamics, winning-losing, and other factors can be very useful. By itself, it's just another incomplete manipulation of one, single statistic to support an argument you want to present.