I have a contact with Thinkware in Vancouver. The F770s are completely out of stock due to high demand, mostly sucked up in the US. It'll change eventually, but the Amazon Canada prices are inflated due to low stock and opportunists.
I have both a F770 set in my car and a F750 set in my wife's car. The F770 is definitely nicer looking in a more compact container and it's all black, with improved wire management so you can completely hide it. The F750, you get one of the wires sticking out a little, and the camera bit is silver in color which stands out.
Both models are identical -- same cameras, same tech. But the F770 has newer firmware that introduces timelapse mode, which is nice, and the gimmicky night vision mode which is junk. People have applied the F770 firmware on the F750 and gained all the new features.
Some people prefer a hidden look like I do (F770), and others want theirs to be easily noticeable (F750). Think of the F770 as a subtle version tweak of the F750. You won't go wrong with either. And a good time to buy these is during Black Friday sales. You can score an entire front/rear/hardware set for about $400 CDN.