Control has changed hands at both Old Trafford and Stamford Bridge since 2022, as Ratcliffe is now overseeing the sporting department at Man United following his 27.7% purchase last December, while Boehly and Behdad Eghbali took the Chelsea reins from Roman Abramovich.
While Man United have spent a fair amount during the Ratcliffe era so far, Chelsea have already surpassed the £1bn mark on signing players, albeit to only achieve mediocre results in the Premier League.
A stalwart of the Man City defence for nine years, Dunne - who played for the Citizens when Sheikh Mansour took over in 2008 - told Sports Mole that Man United are going about their business the right way as opposed to Chelsea's gung-ho strategy.
"With United, you can see that Sir Jim Ratcliffe has adopted a similar mindset where they're trying to improve small little things each time. Improving the tunnel, improving the stand and building the stadium, they'll do it gradually," Dunne said.
"The difference being at Chelsea they've just gone and spent a billion pounds on players straight away. The club needs to be in the right place to progress before you start bringing in superstar players.
"I think that's what Man City got right. They built the club before they started to really focus on making the team so strong. All the money is fantastic, but it does take time."
Comparing Man City, Man United and Chelsea's spending under new ownership
Dunne is accurate in saying that Man City did not hit Chelsea's spending heights during their first summer window under new ownership, but the Citizens still splashed £122.4m on signings in the summer of 2008, including one player who was close to the superstar bracket at the time in Robinho.
Meanwhile, Chelsea's spending in the summer of 2022 reached a staggering £272.4m, as Boehly and Eghbali brought Raheem Sterling, Kalidou Koulibaly, Marc Cucurella and Wesley Fofana to Stamford Bridge for sizeable transfer fees.
The Blues subsequently forked out another £290m in the January 2023 window alone before paying over £400m for new players in the summer of last year, and then surpassing the £1bn mark by bringing in nine more permanent signings for £206.4m this summer.
In contrast, Man United's total spending in their first summer window under Ratcliffe totalled £183m, but neither side has pulled up trees in the early stages of the new season, with Chelsea sitting in eighth spot with seven points while the Red Devils occupy 10th position with six.
Tensions in the Chelsea boardroom are allegedly rising too, as it has been claimed that Boehly's relationship with Clearlake Capital is on the cusp of collapse, but both parties could supposedly have to pay as much as £3bn to assume full control.
Dunne warns Man United, Chelsea, Newcastle fans against "sudden impact" from new money
As well as Chelsea and Man United, Newcastle United also entered a new era under Saudi Arabia's Public Investment Fund in 2021, but that takeover has not led to the levels of spending that some Magpies fans may have anticipated.
The Magpies only brought in Lewis Hall, Odysseas Vlachodimos, Will Osula and Miodrag Pivas for transfer fees this summer, and Dunne has warned fans not to expect a "sudden impact" with new faces at the helm.
Reflecting on the improvements made at City in 2008, the Irishman said: "Everything became a higher quality. The expectations grew a little bit, things got better around the place. There wasn't really a sudden impact from all the money, it was a gradual thing, and you can see it now that the club is still growing, still getting bigger.
"It never went from A to Z in a second, it took time to build what they wanted to do. It took them a few years to win the league, it took them a longer time to win the Champions League.
"It was a period of growth for the whole club, they made themselves a sustainable club where they've got a huge structure. The academy is huge, the clubs involved in the City Football Group, it's all a big business for them. They've done it gradually rather than trying to skip certain phases.
"You've seen it as well at Newcastle, where they've not been spending huge money on players, but I'm sure the infrastructure around the club, everything's getting bigger and they're preparing for a better future."
Dunne - who played over 350 games for Man City from 2000 to 2009 - also provided an update on the future of manager Pep Guardiola, whose contract expires next summer amid links with the England job.
Richard Dunne was speaking to Sports Mole on behalf of Heart Bingo.