One of the local police departments moved from Mini-14's to an AR-type rifle a few years ago and there was a fair amount of screaming from the citizens. It was basically the look of the rifle that was the issue.
Outside of the accuracy argument, the two rifles do the same sort of thing. They are semi-auto in operation, shoot the same round, have close to the same rate of fire if it came to being in a firefight with a BG, and have the capability of using hi-cap magazines.
The city used the argument that the Mini's were old and approaching the end of what they called the service life of the rifle. The city got a grant to help defer the cost of the AR rifles so it wound up being about the same price for either one. One rilfe went into every patrol car and more were purchased for the SWAT Team.
What I found strange is that while people may be frightened by an EBR, they really don't seem to have an issue with local LEO's who shave their heads, wear sunglasses all the time, wear their uni's to look like SWAT teams (there are some local LEO's who even look like they belong in the WWF ring!) complete with bloused boots and flack vests outside their shirts. While I have great respect for LEO's, I just don't see why some of them have to look (and in some cases, act) like SS or SA storm troopers.