They both have slightly different rules. The scoring is mostly the same. Both have 1QB 2RB 2WR, Defense/Special Teams and 1 TE, FD has a kicker slot while DK has a flex (RB/TE/WR) slot. Yahoo has a copy cat daily fantasy sports too, I’m going to try it this week, the salary cap is much lower it seems (compared to player salaries) so you really have to find value players. The DK mobile app is better than FD in my opinion but I like the FD web app better than DK. I mostly use it from mobile so that’s why I went with DK.