A bigger oponent even untrained can punch hard, can be a tough ************ and take the blows, can make it very hard for you to get in striking range without fearing his arms/legsbeeing big he has more range remember that striking, better or worse is instinctive, but the moment you take him to the ground its another world, you can be the size, strenght you want, you WILL pass out to a well aplied choke, your arm will break as easy as the next guy, and if everything fails you can allways close guard and try neutralising him by holding thight to him, he is bigger chances are he will tire faster then you. :cachas:
I think that I disagree somewhat. Someone with better/faster/accurate strikes typically can frustrate a larger opponent in striking. The larger opponent (from my limited experience) will then typically push in/tackle/grapple/grab. I see size as mattering more in this range. You can outmuscle an arm-bar, mount, or hold. You can't outmuscle an evasion, dodge, or jab.