you'd have little reason to care about how big your motherboard is size has little influence on performance on the motherboard level(in mainframes and microchips size does count)The issue is physical compatibility.should you ever want to upgrade the performance of your computer by replacing its motherboard the best possible upgrade out side of replacing the entire computer board size will determine what will fit in your case.if you are daring and want to save a few hundred dollars by getting a real lesson about how really simple PC's are by building one youself you will need to know that size inbox to put put every thing in.once you know motherboards are different sizes,the rule is in tuitively obvious,if you have an XT size case you will need an XT size motherboard.
