depends really. Do you have a Strix RGB graphics card?
If so, then getting the Strix board is what you should do so you can synchronize the lighting.
Otherwise, they are both budget options and both on par with each other, so pick the one that has the one or two features that the other doesn't that's more important to you.
If you don't care about the little extra features because you don't use hardware that utilizes these typically useless features for the average consumer, then pick the one you think would look cooler in you system.
I don't know what country you're in, but if the price of the AsRock B450 Pro4 ATX (not the mATX) is within reach, then I'd recommend that one probably. For me here in America the price of the ASUS is $123.91 and the Aorus Pro Wi-Fi is $123.98 but the AsRock Pro4 is $79.99 and the AsRock Fatal1ty Gaming K is $100.88 and for me the choice would be to either get the Pro4 and save some money or get the Fatal1ty and save money still but not as much money and get the awesomeness that is the Fatal1ty board.
Otherwise my choice of board is ASUS but I prefer the higher end ones.