Scottie or Rory? World No.1 or World No.2? The former is the clear favorite in the betting for The Open.
However, McIlroy, who won The Masters in April, cannot be dismissed after shrugging off his Grand Slam hangover, especially after slipping comfortably back into links mode at the Scottish Open last week.
In fact, the latest statistics from Clippd suggest the Northern Irishman might just have the advantage over his American rival going into the final men's Major Championship of the season at Royal Portrush.
The two best players in the world (based on the Official World Golf Ranking) have taken the game to a new level over the last couple of seasons.
Although McIlroy hasn't won a tournament since The Masters in April, his last two performances suggest that he's back to somewhere near his best.
After missing the cut at the Canadian Open in June, the five-time Major winner recorded a top-20 finish at the US Open.
He was clearly still a couple of gears off it at Oakmont, although he tied for sixth at the Travelers Championship and was just pipped to the post at the Scottish Open last week.
Scheffler, meanwhile, who said this week that "golf doesn't satisfy me", remains a model of consistency.
Remarkably, Scheffler has not finished outside the top-10 since March. During this spell, he's racked up three wins, including the PGA Championship in May.
With results like this, it's obvious why he starts the week in Northern Ireland as the hot favorite, with many believing he'll get his hands on the Claret Jug at least once in his career.
Even so, it's a hard one to call. McIlroy has an Open Championship victory on his CV, and his performance in Scotland showed that his game is in very good shape.
Scheffler, however, who finished tied eighth in North Berwick, was not far off the pace.
You know all this. You're a punter and you want to know who to back - so is there anything we can learn from the statistics?
According to Clippd, both players have identical overall Player Quality scores of 105 - five points above the tour pro average.
It's when you drill down further that it gets more interesting, with the recent data actually coming out in favor of McIlroy.
The American is comfortably ahead in the iron play category and just clear around the greens, but McIlroy has the advantage both off the tee and on the greens according to Clippd.
The data shows that McIlroy is stronger with the flat stick in hand in the crucial 3-15ft range, is nearly twice as effective in Strokes Gained: Putting over the last 20 tournament rounds and has fewer putts overall.
Clippd sums up how McIlroy could well have the advantage this week, saying: "While Scheffler's iron play excellence keeps him highly competitive and directly addresses Royal Portrush's most obvious challenge, McIlroy's advantages over the last 20 rounds in three of the four key performance areas — driving, short game, and putting — create a compelling case for the Northern Irishman's prospects.
"The data suggests that when the championship reaches its decisive moments on the Dunluce Links, McIlroy possesses narrow statistical advantages that could swing things his way.
"Whether those numbers translate to lifting the Claret Jug will depend on execution under the unique pressures that only golf's oldest championship can provide.
"For golf fans and analysts alike, the statistical backdrop promises a compelling championship where two different approaches to excellence will be tested against one of golf's most demanding venues."
Read Clippd's full breakdown of how Scheffler and McIlroy compare statistically
