"They both just got huge paydays in China, they may be putting a slight front on that camaraderie," sports psychologist Dan Abrahams told CNN.
"In a sport like golf, having a spat with a rival isn't seen as being the right thing, whereas (in soccer) Alex Ferguson having a spat with (rival manager) Arsene Wenger, that seems to be quite normal."
Abrahams argues some of McIlroy's older European peers such as Luke Donald, Lee Westwood and Darren Clarke -- who have won only one major title between them -- may have suffered from their on-tour friendship.
"Speaking with a lot of golf coaches, that generation have been perhaps a bit too friendly with each other," said Abrahams.
"If you compare them with Nick Faldo, he was renowned for keeping himself quite isolated, which was a catalyst for his competitiveness. I think keeping your distance from competitors can be a useful thing."
Faldo has questioned the apparent friendship of golf's two biggest names, but McIlroy played down the criticism.
"You're on tour long enough and you don't need enemies out there, you want to have friends," the Northern Irishman told CNN.
"Life on tour can get a bit lonely at times and you wanna have guys that you can go out for dinner with. You're seeing most of the guys each week and you've got to have someone to talk to. If that's what worked for Faldo then great, but I don't think it would work for me."
In the high-octane world of Formula One, Alonso is known for his clashes with fellow drivers -- he left McLaren after only one season following a bitter feud with teammate Lewis Hamilton.
However, this year the Spaniard has been much more respectful of Vettel, despite Ferrari's united front in downplaying the achievements of Red Bull's history-making triple world champion.
Rumors persist that the Italian marque wants to sign Vettel for the 2014 season, which would be an acid test for relations between the two drivers.
"When you get two No. 1 drivers together with no team rules, then the sparks can really fly," says Tu, who has worked with Ferrari and former F1 world champion Jackie Stewart.
"It's rare for them to be good mates. They may get along, they may trust and respect each other in a professional capacity, but hanging out is a different issue."
Seven-time world champion Michael Schumacher, who has now retired for a second time, was known for his win-at-all costs approach at Ferrari but such an attitude is becoming increasingly unacceptable for sports fans, says Tu.
Contrast the feelgood factor of the London 2012 Olympics with the demonization of Lance Armstrong, who has refused to contest allegations of systematic doping during his time as cycling's tour de force.
"There is, at the moment, a very fine line that sport is treading -- this desire and ambition to win, but not to do so at all costs," says Tu.
"Someone like Schumacher, his desire to win would take him to the dark side. That type of willingness to do whatever it takes is a feature of champions. Unmoderated, it's pretty dangerous for the game.
"We've just been through a period of excess and egregious behavior from many corporates -- but equally sporting teams as well. The desire to win, and the merits and rewards of winning, maybe outweighed the joy of winning.
"I think sport is recalibrating. That's why the Olympics made everyone so happy. There was a sense that winning was important, but not necessarily at all costs -- it's the sportsmanship sometimes that makes the bigger story."