I tell you, forgot both devices. Buy yourself a Raspberry PI unit and load XMBC on it. You'll never look back again.

@Rocky Stefano: There's no way that a RasPi is going to appeal to any non-technical people. Not only that, it's not a pretty device with wires coming out of every which way. And while the base unit costs only $35, the total cost after buying the SD card, a power supply and peripherals will be around $80 or more depending on peripherals. Then you have to factor in configuration time and research.
Other than that, this article doesn't mention that AppleTV is a closed system. It's basically Apple's way of getting iTunes into your living room. In contrast, the Chromecast has an open API that anyone can build apps to utilize. Give it a few months and you'll see how many apps are supported (like Plex).
The more apt comparison for Chromecast would be to something like a Roku.

"Side loading" content is easy on Apple TV. The only thing to consider is the content needs to be imported into your iTunes library. The extra step of conversion may SEEM like an inconvenience, but it removes any problems with video files not being able to be displayed by AppleTV. Today there are so many good methods for automatically converting and importing into your iTunes library to make them available on your AppleTV it is ridiculously easy to do so. Some software suites like Vuze have it built right in. Android devices can also stream to AppleTV. There are many Android apps that allow Android devices to use Airplay. Here is something else to consider. Does the Chromecast device allow you to plug in an Ethernet cable? The AppleTV does.

I think this is a well done comparison. I think it depends on how much one wants to pay and what one is getting out of it.
I think if one goes the Raspberry Pi route, they will probably also be able to create a case for it too. I think it is a creative alternative to anyone is like to make things like it. Perhaps one day a person could create something using a Raspberry Pi and sell it either as a kit or already assembled. It could be an alternative to the above two.

Not "mobile device slinging" is the GREAT advantage of the Chromecast device. When you send through a phone, you will likely be paying for data. Chromecast uses a home wi-fi network directly, which is usually free at this point.

I can see this having the biggest impact on the "Smart TV" market, which is already being threatened by Miracast. One very appealing thing about Google Chromecast, for me, at least, is access to YouTube, since my Rokus do not have that application. YouTube has many documentaries and even some feature-length films that are not available from any other source.

Well, if you have a modern TV then it has most of those apps that these have. I think my TV has a lot of those that the Apple TV has and then my bluray player has a few that my TV doesn't and then my left butt cheek has a few that those don't have. Seriously, why does anyone need either of these if they have modern equipment? Just to watch a TV you need a TV and that has a lot of those services. You want to watch bluray you have to have a bluray player and every bluray player has some of those services. Then, if you have a game console of any kind you have more services than these have. I'd rather have a device that can run XBMC hooked up to play my ripped files the way I want because I already have all these services on one of my already owned electronic devices.

$35 for YouTube and Netflix streaming to any HDMI TV, no need to say more. I am in.

My solution has been to own a Playstation 3, which has a superior Netflix interface, all the other online options the hockey pucks offer, plays DVDs and Blu-Rays as well, and is also a video game console.

Power? 'proprietary cable'? A common 2 pin power cable found on radios, razors, power bricks for hard drives, etc.