Video quality is not that big of a deal, especially daytime quality. I have used various resolutions on my dashcam, and anything HD (720p) and above is good enough. It can capture enough video detail to get you out of trouble is you're involved in an accident. Which is why we have dashcams in the first place. The nighttime quality, I think, is the only important one to consider. I've checked videos on Youtube, and it looks decent enough for that.
Here's a video I captured in 720p using an LG G2 Mini attached to a cellphone holder and running the CaroO Android app (before I bought my dashcam):
VIDEO
Even with the low HD resolution, it can capture decently good daytime detail to see the almost-accident. BTW, excuse my profanity.
So don't worry too much about video quality. You're not filming a movie. Keep that in mind.