What is the difference between these two modes?
Samsung's MU 2017 models have the HDR+ mode in the picture settings menu whereas the NU 2018 models (most of them) doesn't.
HDR+ on your TV is a faux HDR effect mate, It attempts to map the current source into the native range of the panel. Invariably this leads to an unatural oversaturation of colours, also the extra brightness increases the likleyhood of other issues such as haloing.
The only way it would add extra detail to the scene would be because the TV was poorly calibrated in SDR mode.
I would recommend leaving it off