I just finished my Purist run through and I had far less detection sounds coming from guards than on my Expert run. Granted it was auto patched before I started my Purist play through, since I have the Steam version, but it seems to me Purist is dumbed down in detection a bit due to having no HUD indicators.
Can anyone that's played on Expert and Purist before the AI patch jump in and give a testimonial on this? I was hoping to build up toward a really challenging play through, but instead was shocked at how easy it was. In Train Station I only had to use Instinct for a few seconds while actually boarding the train.
I suppose the next thing is to do a suit only run through the whole game, vs just segments of it.