Well, I could be wrong as things have changed since I last bought a TV (3 years ago) but generally plasmas have a glass screen and many LCDs didn't, hence they could have the non-reflective finish.
Iirc many plasmas have anti-glare finishes but only work so well, but to reduce reflection to a complete minimum an LCD with a matte finish is the way to go.
This is what I read up about when I bought mine anyway, it could all be complete b****cks now if technology has moved on.