And I believe the 600Hz refresh rate of plasmas isn't a comparable stat to LCD's refresh rates. In general, plasmas do have less motion blur, but I don't think it's something your really going to notice much of a difference with for the Vizio at 120Hz. Most reviewers agree that 240Hz really makes no big difference between 120Hz, so don't buy into that market hype.
That said, I have a Panasonic plasma and love it. It's 2 years old I think and it's been great. I trust Cnet's reviews as well. With a lot of natural light though, you may want to consider the Vizio as LCD's get brighter. I've never really read about a good breaking point for when a room is too bright for plasmas. That said, if you buy from Costo, they have pretty stellar return rules, so you could try out a plasma and see if it's ok.
The one thing I recommend too is to check cnet's calibration guides to get the best picture quality. See link for Panasonic's
If you have a large bank of windows in the room, you will probably end up with a reflection off of a plasma's glossy screen. Usually it's not noticable, but in dark scenes, it can be.
LCDs and LEDs generally have more matte screens that diffuse the glare better than plasmas.
spring the extra 200 dollars and get 5 more inches, Better picture quality, and a smart TV.