You're twisting words somewhat. An average punter probably wouldn't notice if you started playing clean bass instead of distorted bass, unless the particular track is entirely defined by that sound. So no, clearly they aren't going to pick up on changes brought about by a compressor, and not at deafening gig levels. Does it make a difference in a live mix? Absolutely, otherwise I wouldn't waste my money buying and using one! But you're right, solo'd in a sound clip even a punter would recognise the difference