2020ish X3M vs X3M40 running costs how do they stack up?

I’m really torn. The delta in price between similar mileage and year x3m vs m40 is not enough to really sway em one way or the other. It seems like an x3m is the better choice. I keep my vets for about a decade. I always buy used (we live in manhattan so cars are only used weekends and get maybe 5000 miles a year - highway at that). I have a very light foot these days so gas mileage doesn’t matter.

So realistically is there a stratospheric cost difference Maintenance between the two. All of the ones I’ve looked at were about 55-65k miles. I’m paying cash so loan rates don’t matter. My USAA full insurance is only about 35 dollars a month difference. Would there really be a big savings for the non M car? Am I missing something. Is reliability very different? I recently found out my neighbor has a 2019 xM3 M40 with well over 150k with zero issues.

Is the XM3 similarly reliable? I am an engineer by trade so I tend to maintain my cars to the highest levels changing all fluids before due.

So am I missing something or is an X3M going to have similar running costs as the M40?