I think in most cases they are interchangeable. When 似る is combined with 合う to form 似合う you wouldn't use と. But I think in the case you gave above, the meaning is virtually the same no matter which particle you use.
I think there is some difference. The way I learned them, と emphasizes mutuality, while に is more one-sided.
AはBに似ている = "A looks like B"
AはBと似ている = "A looks like B (and B looks like A)"
For example, a situation where と can't be used is when you say "My sister looks like Angelina Jolie." The relationship is not really mutual because you would never say "Angelina Jolie looks like my sister.".
My wife also thinks there is some slight difference. She explained it and I promptly didn't retain it. It had to do with the coverage of what was 似ている. I pictured a Venn diagram. This is the kind of thing I don't bother "learning" any more. Either I pick it up or I don't.