I just ran a little test. If the block adds any drive, which some time-based effects add, there won't be perfect phase cancellation. I split the signal from the amp into two separate chains that had exact duplicates of a cab block and a delay block. In their default state when set before or after the cab, there is perfect phase cancellation (any configuration). If you add drive to the delay (hand typed, same amount), the phase cancellation is imperfect when one is set before the cab and the other is set after the cab. I believe some delays adds some sort of harmonic distortion by default. Maybe other blocks too. I haven't checked.
The difference is probably negligible unless settings are extreme. I assume the configuration set after the cab block will be brighter due to the added harmonic distortion not being shaped by an impulse response