There is no difference frame-wise. Negative guard breaks only exist so it visually makes more sense. For example Eliot's 46P is a negative guard break but because it visually looks like such a strong attack they gave it guard break properties.
Free Step Dodge
KING JAIMY
XxNoriakixX
Eliot's 46P is +2 though
Force_of_Nature
Yeah, like KING JAIMY mentioned, it's the same frame advantage. The difference lies in the move's recovery frames. A -5 move with short block stun will recover quickly (like around 20-25ish frames give or take for example), whereas a negative guard break could have 40+ recovery frames for instance. How would a move with 40+ recovery frames look on block to be -5? The guard break block stun was the answer.