mini display port connection

Sometimes when I reconnect my laptop to a dell u2312hm monitor via a mini display port cable, the display drops to a 640x480 resolution on the external monitor and I cannot change this for the external monitor but I can change it for the laptop display. This only seems to happen when I connect the monitor to the laptop and turn the laptop on or some other rare occurances. To fix this problem, I have to plug in the vga cable (This changes the resolution setting back to 1080p) and then the mini display port and then unplug the vga cable after which the resolution stays at 1080p. Anyone one know what the cause of this problem is and how I can avoid/solve it? Also in terms of image quality, are there any noticeable differences between vga and mini display port?

 

I would try using Win + P, setting it to "Disconnect projector" and then back to extend or projector only (depending on what you use) to reset the connection. I would prefer mini display port over VGA connection but that just might be my bias towards what's new, digital and modern vs VGA which is ancient :|

 

Thanks. I will try that.