Miami 27
Jacksonville 13
I think that the only legitimate reasons to be afraid of this game are your fear that 'Dolphins gonna Dolphin' and the unfortunate reality that **** happens.
If you watch these two teams play football, you can see that Miami is more talented across the board -- particularly on defense -- and has much better play from the quarterback position.
Statistically, Miami is a much, much better football team than Jacksonville. Football Outsiders ranks Miami as the 10th best team in the NFL in total DVOA, while Jacksonville is ranked 31st. Jacksonville has the worst offense in the NFL by pretty much any metric you want to use, and it's really not even close. Jacksonville simply can't score points and turns the ball over a lot. Jacksonville's defense also wasn't very good for most of the season, though they did beat up on the Cleveland Browns this past week.
Jacksonville's big hope in this game is to get a lot of fumbles. As long as Jarvis Landry cleanly fields punts, and our skill players hang on to the football, we should be fine. Jacksonville has not been good at creating interceptions.
One final note on why I am confident Miami will win, the Jaguars played against Philadelphia in week one and gave up 34 points, despite the Eagles handing them multiple first half turnovers in what was a very sloppy performance. The Jags struggled to stop Philly's inside running game (an area where we are similar) and that was with their best run stuffing linebacker, who won't be playing for Jacksonville on Sunday.
Anything can happen on Sunday, but the truth is, Miami is just playing much better football than Jacksonville, is a more talented team, and should win this game by double digits.