Waver Velvet may be a top scholar of magical arts but even he would be the first to admit that he’s not very good in combat. Shirou has obtained many more powerful abilities over the years and is the more complete fighter. I would also say Shirou has a stronger grip on his own ideals and could have verbally crushed Waver if he wanted too. There’s no avenue towards victory for Waver here. Shirou wins.