"He's an amazing Bruce Wayne, let's just be frank about that. And then when he puts the cowl on, you know he's got the chin for it," Snyder tells PEOPLE while dishing about his (and the Batmobile's) role in this year's Doritos Crash the Super Bowl contest.
While the director acknowledges the casting raised some eyebrows from fans (and even Affleck himself) early on, Snyder says he always knew he had the right man for the job.
"Casting Ben felt like a no-brainer to me," he explains. "I know that there was some backlash, but he's just so perfect to me, especially in his size and his age."
Check Out the 'Batman v Superman' Posters
The Batman Affleck portrays in Batman v Superman is loosely modeled after artist Frank Miller's version of the character from his comic book, Batman: The Dark Knight Returns. In the graphic novel, Bruce Wayne is already in his 50s and on the verge of retirement. He's also depicted as taller and more muscular than in other illustrations.
"I'm sure once the fans discover it, they'll feel the same way I do," he adds. "He's certainly got the chops for it, so I didn't quite get the initial reaction."
When the first images of Affleck in the costume hit the web, fans began to see things from Snyder's perspective. "I took that picture of him next to the Batmobile," he remembers. "When I looked at the back of the camera to see what it looked like, I was like, 'Holy s---, that is ridiculously perfect.' "
Speaking of the Batmobile, Snyder reports the new ride can be driven in real life, although he's not exactly sure if it's street legal. In fact, the lucky finalists from this year's Doritos Crash the Super Bowl contest got a chance to take a spin in the legendary car with Snyder himself.
The contest selects the best homemade Doritos commercials and gives a $1 million grand prize to the best director. Plus, the winning ad will be played at this year's Super Bowl.
"It's a privilege to me to be around these young talents," Snyder says. "All their videos totally crack me up."
Batman v Superman hits theaters March 25.