Perception or not I think the truth is there.
The difference, at least 'A' difference, as I see it is that Fox News whether it be their straight news portions but especially their commentary shows(O'Reilly, Hannity etc) make no hidden notice of giving a conservative angle. It's blatantly clear in the commentary shows and only there in some minor instance for straight up news reporting. Most have a hard time discerning this separation of news vs commentary portions on Fox.
The rest of the media from the alphabet's down to PBS like to bill themselves as being middle of the road on all points and the last 10 years they clearly are not. The last 5-6 years especially. When there are reports of editor offices donating 80% plus to Democrat causes and trying to pass off phony documents as real like Dan Rather did the bias is clear. When swarms of reporters stalk out every facet of Sarah Palin's life but sweep Biden under the rug it's very clear where these guys interests lie. Biden makes Palin looking fucking brilliant and that includes silly comments like "seeing Russia from her house". Man has a foot in mouth gaffe almost monthly but weekly on a campaign trail.
But really in a nation with so many news options PBS as a news outlet is obsolete. I believe in PBS programming from NOVA, their documentaries on through SStreet but funding for them as a news outlet is long since past.