All of the listed model with exception to the HU8550 are curved. Of which the HU7250 is the lower series which lacks 3D. This also hinders its imaging quality when refreshing an image. This is what changes the CMR—Clear Motion Rating which is an important process Samsung uses to produce a smoother more clear image. Therefore, I would highly recommend stepping up to the HU8550 (which increases the CMR). If you like the curved look and those models would fit nicely in your space the HU8700 improves with a feature called "Auto-Depth Enhancing" a process that allows the viewer to have forced perspective with anything they are watching. The ultimate reason to jump up to the HU9000 is for the detachable One Connect. This is nice if you plan on wall mounting because your connections can be located away from the TV—which means never having to reroute cables through the wall. There are other various "small" differences: CMR, color palette variety, micro-dimming improvements, top mounted camera (on the HU9000), etc.

Note: I'm an owner of a 65" HU8550 and have 1yr. Sales Experience at Best Buy with the Home Theater department.

***For a better picture look into Monster HDMI cables or AudioQuest HDMI cables, as they are made for the future and will ensure a great picture. Also, surge protector and power conditioner...dirty power flowing in can slowly wear your TV down and affect picture quality.***