The one feature I like with FanDuel is the incorporation of the live scoring into the my bets screen. So if you have a parlay, you can see the score of each game without having to go into another app or another screen within the app. DK just shows the result when the game ends.
Also, the way FanDuel and Draft Kings handle free bets from promotions is different. FD gives you site credit, so when you bet a credit you get the win + the credit. With DK, they only give you the winning amount. So if you use a $10 credit in FD, you'd get ~$19 with a -110 win where DK you'd get ~$9.