Currently, there is no Skype on the Chromebook. You can use GoogleTalk instead.
If you buy the Acer Chromebook, you can connect it to a large screen TV via the HDMI connection, which carries both video and sound in digital format.
If you buy the Samsung Chromebook, you can connect via the VGA port, which is only video, and you have to connect audio separately. Both are analog signals.
I like the Acer better because of the HDMI port, its better screen at 1366 X 768 pixels (true 16:9). It's battery and memory are user-replaceable, whereas for the Samsung, they are not.