"Katie and Tom also have very different parenting views," maintains the Radar spy. "Katie wants Suri to go to school with other children and have a grounded routine, whereas Tom doesn't."
Suri, whose late nights, lipstick and high heels have raised the hackles of the parenting police, is rarely seen with kids her own age, and her meltdowns are often captured by the ever-present paparazzi.
"Tom is nowhere near as strict as Katie is and doesn't believe in disciplining Suri, whereas Katie believes that is important," continues the source. "Tom basically treats Suri as a little adult. However, Katie treats her like a 6-year-old child, and that causes some major clashes over parenting style."
The Daily News source echoes this assertion, with a source citing "issues raising Suri, different ideas of parenting" for the divorce.
It may be telling that Holmes, whose attorney father just happens to practice matrimonial law, opted to end their prenuptial agreement-protected marriage in New York rather than California.
In a New York court, she could get into specific issues (like, say, Scientology) over why the marriage is broken, potentially shoring up her custody case.
If she were to get sole custody, she would be able to make decisions on Suri's schooling and religion.
"Katie has no plans to contest their prenup," continues the Radar source. "The only potential area of conflict between Tom and Katie is custody of Suri. Katie will absolutely never agree to a situation as Tom had with [Kidman]. Katie wants Tom to be a big part of Suri's life, and he is a great father, but she wants to be the primary custodial parent that raises Suri."
But Cruise, who turns 50 on Tuesday, is expected to put up a fight. Read on for how he might do it …