4E is exception based. All classes get the same base modifiers, while other factors are going to alter those. What's making the difference is powers/feats selection, really.
If the OP was wondering about the "real" effectiveness in hitting someone while fighting, it would be something to talk about.
The fact is, in 4E, a basic is just that. One basic swing with your weapon (something you'll be basicly using only when taking AoO the most, or otherwise not really often). Consider in 4E full round attacks are totally gone, that's a major point. Now the real difference between what a class can and can't do well, lies in its powers.
With powers out there to make the difference, you see the point in getting rid of different BAB rates. You can't really make assumptions at the numbers without taking powers into account, for the matter of this thread.