I also in general prefer LCD's, but if you do a google search on the particular model of vizio Plasma that you are considering, you will find that they are very well received. I believe that all their plasmas incorporate the Faroudja DCDi processor so they are very good at resolving SD content as well as HD. the 47" 1080P model does not use the Faroudja processor and as much as I like that TV, you will definately notice that it leaves a bit to be desired when viewing SD content.
With that in mind, you have to decide if you are ok with a somewhat sub-par SD presentation, but good HD quality with 1080P input capability if you are considering their LCD. What content will you be watching most frequently? Do you play video games and are you likely to experience burn-in?