I've not heard of particular reports of police problems.
My personal opinion and not supported by fact, is that IWB is a little more acceptable to some people. I think they feel you must be someone that has permission to carry if it's IWB.
I did some experiments a long time ago and found some things get noticed less. Black holsters tend to get fewer stares than brown. Cross draw gets more attention than strong side.
Auto's get noticed less than revolvers...Etc.
I may try IWB vs OB one day.