Leaving your guitar in a stand is very dangerous as it can get knocked over, but the more serious issue is it exposes your guitar to small ambient air changes and humidity changes 24/7 like being near a vent or exposed to sunlight, near a fireplace. Hanging it on the wall is the same as your guitar is constantly being exposed to small changes. Always store your guitar in a humidified case whenever possible if you don't want issues long term with warping and eventually cracking.