Well, you're going to find lots of folks eager to tell you about their bad experiences with any given brand. Last time someone put up figures for reliability of the major brands, nothing stuck out particularly.
My own experience is that my 7 year old Vizio is still going strong, although relegated now to the study (it's only 42"}. OTOH, my 65" LG 65LW6500 developed a vertical line right at the end of the warranty period, and I did report the problem. Got the runaround from LG, and of course during that time the warranty expired. They plain wore me out. Since I was fairly certain what the problem was (TAB bond failure), I had a go at fixing it, successfully. That being the case, I didn't pursue the matter any further, but they're in my bad books. Does that mean you also should avoid LG? No, of course not.
As to the original question: Chances are a Vizio 3D (passive) TV is going to have an LG panel anyway. They make none of their own parts. Assuming an LG panel in both, black levels and contrast are going to be mediocre, at best. Passive 3D has its supporters and detractors, but it looks surprisingly good, to me. My LG has a pretty good onboard media player. Dunno how current Vizios compare in that department. 240 HZ vs 120 HZ is over-rated, IMO. The 240 likely refers to backlight scanning only.
Personally, for comparable models, and especially since the Vizio is a couple hundred less than the LG, I don't see why the Vizio wouldn't be a reasonable choice. Go have a look at both, if you can.
Good luck whatever you get.