That question makes perfect sense and as far as I can tell. There is no difference. No loss of image quality. Just keep in mind that the quality of the photo will be based on the quality of the video..
4k+ video=4k+ photo
1080p video=1080p photo
The quality is similar. If you fly 4K you will have the closest quality. I have noticed on the EVO and my digital cameras that when you take a photo within the video the autofocus may be slightly off, but it is close.
If you know you want a crisp image always move to the native photo portion of the app.
For best results you will want to shot in RAW photo mode. There are paid programs out there that will take the best frames of your video and turn into a HDR photo but I find them very resource heavy on my computer. One such program is called HDRinstant.