which make/model is your 42" HDTV?
It's hard to say for certain unless we can actually compare two models' specifications.
IME and HO, the vast majority of Vizio HDTVs have generally less than ideal PQ compared to other name brands. If you have ever compared them side by side you could notice this. AFAIK they still do not offer true 120Hz, which is why they advertise it as being an effective refresh rate. Here are some hopefully helpful links: