The nice thing about the Acer is the HDMI port but for me VGA is better for most monitors and projectors I use on a daily basis. The Acer is a bit smaller and lighter but loses some battery hours. It is all a trade off. Personally the Samsung looks better but beauty is in the eye of the beholder.
We have both an Acer wifi and a Samsung wifi chromebook in my house. I have the Acer, and my brother has the Samsung. The HDMI port and price difference made me go Acer. I've played with both and they're pretty much the same in my opinion. The Samsung feels a little bit sturdier and has a much better touchpad. If you have any specific comparison questions, I'd love to help out.
I'd rate both of the chromebooks about the same from a performance perspective, but the Samsung one is definitely the sexy one.