It happens at every farmers' market once summer corn is in season. Now that it is, every farm that sells corn has to deal with obsessed shoppers ripping back corn husks looking for what they think is an optimally ripened piece. There are other ways to tell though, apart from tearing back corn's clothes.
Obviously, a bigger ear of corn is better if you want a bigger ear of corn. It'll have more kernals, but bigger isn't always better when it comes to summer's sweet crop. What matters is that the cob has no holes or missing kernels. You don't have to go all toddler-on-Christmas-morning to find out. Instead, just feel for divits and soft spots that might have resulted from worms or uneven ripening.