It’s a different circuit design meant to recreate the original but I highly doubt on a stage the audience is going to care which model you’re using.

I’ve never done a side by side comparison though, no, although I do know that the knob positions do not match up between the two units so need to be adjusted accordingly to achieve the same sounds, that may be where some of the reviewers went wrong.

The original and reissue are different in a number of ways:

-The RI is in stereo. Both outputs have a fixed blend of wet and dry signal with a phase difference in the effected signal creating a stereo effect
-The Original has a mono effect output that can either be a fixed blend of wet and dry signal, or a 100% wet signal using the blend slide switch. It also has a direct output to allow you more control over the wet/dry mix
-The Original when 100% wet in chorus mode with minimum delay time allows for a decent triangle wave vibrato, something that the RI cannot do
– The layout of the knobs is different between the units
– The Tune knob (called Tune/Delay on the RI PolyChorus) is reversed on the Original. Minimum delay time is clockwise 100%

But I agree that most people will not recognize the difference in a live performance. For that matter, you might save yourself some cash and just pickup a Small Clone if the goal is to sound like Nirvana.