They are both Fangraphs
https://www.fangraphs.com/standings/playoff-odds/about
To generate the playoff odds, we take the current standings, the remaining schedule, and each team's projected performance. We use those inputs to simulate the remaining season 20,000 times. We aggregate these outcomes to find the probability of winning the division or a Wild Card spot, along with winning the World Series and various playoff rounds. If a team has a 90% chance to make the playoffs it means that 18,000 out of the 20,000 simulated seasons end with the team making the playoffs.
[SOS] is our estimation of the difficulty of each team's remaining schedule. We take the average neutral-opponent winning percentage of each of a team's remaining opponents, weighted by how many times the teams play. This is affected by the projection mode -- if you select FanGraphs Projections mode, strength of schedule will use opponents' forward-looking projections, rather than their performance in the season to date. Note that the winning percentages used for each opponent are not the same as the "ROS W%" column. That column takes the remaining schedule into account, while SOS calculations are performed on neutral-opponent win percentages (which you can find on our projected standings page).