Hi,
How large is the difference at the first iteration?
My expectation here is that they compute the same thing but because of floating point errors, the value they return is slightly different (order of 1e-6).
Then when you do gradient descent, you will take a step in that slightly different direction, leading to different gradient, etc. And the two models will diverge from each other.
This is quite expected, even though they get different weight values, they should converge properly to similar final losses (assuming your model is properly stable like most CNN).