I've never seen a TV that has Netflix/YouTube built-in that doesn't have a horrible interface. The [low] cost may be worth it just for less pain.
Chromecast is nice - and novel in a few fun ways - but I just don't see it changing the world, especially since most of its target demographic is somewhat tech savvy (smartphone owning Netflix subscribers) and therefore quite likely to own at least one of the above.
The Apple TV is the worst of both worlds because the remote is required but is smaller than any other remote out there so that it's very easy to lose.
Using WiFi also means line of sight isn't necessary which is a nice perk.