I don't think there is a lot of variance in televisions when you lock into certain price points.
In the $700, you are in the low-mid tier for televisions. I like using the Best Buy website as reference for pricing, but it all boils down to similar statements that continue up to the higher prices. As you get away from Sony, Samsung, and LG, you will find pricing tends to be less, but quality control and support can be more dodgy. So, I tend to stick with one of the three majors. I avoid LG in general, but that's my choice. I think Samsung is a great direction at this price point as you should get decent quality and reliability for the money.
I would probably go look and read reviews of the Sony X80K series and the Samsung TU8300...
Compare the Sony X80K/X80CK and Samsung TU8300 TVs
www.rtings.com
TVs are an area where you do tend to get more as you spend more.
On the off-brand list, the Hisense U7H series may be a great way to go to get more image quality for the money. This TV may not have a 10 year shelf life like Sony or Samsung may have, but if there is a chance the TV will be swapped out (more money in the future), then lasting a decade may not matter quite as much, and quality should still be on point...
I picked up a 58" Hisense LCD for a guest room in my home. Got it from Walmart for under $300 out the door. It doesn't compare to the Samsung in our family room, but it certainly does an acceptable job and works fine for just watching TV. But, the jump in quality you start to get as you pay more will show through with better motion handling, better contrast, and better colors.
If I'm buying for myself, I tend to look for the best deal, and that would be the Hisense. If I'm buying for others, I tend to go for the highest reliability, and that would be the Samsung or the Sony.
As is sometimes the case, Costco, Sam's Club, and Walmart may offer pricing that is a bit better or have an extended warranty or something else to sweeten the purchase, so look around for best pricing or a model which is on sale for a ridiculous price.