This really all boils down to what you and your family is looking for in a TV. You did hit the nail on the head with the differences you mentioned, but the C8000 also offer a higher Dynamic Contrast Ratio (8,000,000:1, vs the C6900's 7,000,000:1). Although the numbers are off by a million, that million contrast does make a difference in the colors and picture quality. The C6900 actually also offers a feature called HotApps that is not available on the C8000 (which instead offers Yahoo! Widgets along with Samsung Apps). HotApps is a Best Buy exclusive feature only found on the C6900 and C670 that adds additional applications to your Samsung Apps library (CinemaNow and Napster to name a few).
My personal opinion on 3D is that it is not a fad at all. All the manufacturers are pushing very hard to get this technology into their consumer's homes. With cinema going the way of 3D, more and more content will be shown in a 3D format. You already have cable and satellite channels that are 3D, and you have several Blu-Rays that will be coming out in the near future that offer 3D content.
I understand that currently, there may be a lack of 3D content, but since the Samsung 3D TVs offer adjustable 2D to 3D conversion, you can easily convert your 2D broadcast into 3D. That may be something to consider.
We are very confused on which tv to purchase (UN46C6900 or UN46C8000). I understand the differences between the tv's; the C8000 has 3D and also has 240 herz. I believe they both contain precision dimming, which from what I've read online is a good feature to have. As far as the 240 and 120 herz, I personally can't tell the difference. I've also been told my a few friends that the herz rate between the 2 does not make a difference..just not to go with the 60 herz for the size we are interested in buying. I am also confused as to spend the extra $$ on the 3D b/c personally, I think it's just a fad (not trying to offend anyone) but I could be wrong. Now when we look at both models in the store, they are not directly next to each other or even near each other so it's hard for us to tell the difference while watching them. We do feel the C8000 has a beautiful picture and color when we watch it but are wondering if the 240 herz makes the picture on the C8000 nicer than the C6900? I do know the 240 herz is the refreshing rate. Does this have to do with picture quality in general? Right now the C8000 is located near the C6300 so I can totally tell the difference between those 2 as the C8000 colors are more vivid.
Basically, I am wondering if it's worth it to spend the extra $500 for the 240 herz, regardless of 3D. Do you feel the specs on the C6900 at Best Buy (C6800 at other stores) are similar to the C8000 (as for clarity and color of picture) excluding the 3D?
Sorry if I sound confused by all this. I just want to be sure before I spend the $$ for either TV, I understand which is better and why. I know when I spoke to one guy at the store, he tried getting me to buy a plasma which we do not want b/c we like the flatness of the LED and when I went back to the store, I had another guy talking about last years models to me... Why he did this, is beyond me and my husband got frustrated and walked out b/c I specifically asked questions in regard to the models referenced in this thread.
Thanks for all your help in advance.