The 10w-30 oil is the thicker oil which will flow much slower through your engine at lower temperatures.
The 5w-30 oil is thinner than the 10w-30 and the 5w-30 oil will flow much faster at lower temperatures.
That's why it's important to use the correct weight of engine oil in different temperatures to make sure your engine gets the oil and lubrication it needs from that oil properly otherwise you risk engine damage which can be costly.