I would like to learn and dive deeper into manual/program mode.
Look at the mode dials on the top of the two cameras. IMO, it makes the Sony DSC HX9V the clear winner over the Nikon Coolpix S9100, because the dial on the HX9V clearly shows the PSAM (Programmable auto, Shutter-priority, Aperture-priority, and full Manual) modes, while the dial on the S9100 only shows scene and automated modes. If you want to take control over the exposure with a camera, the PSAM modes give you the greatest freedom to do so.
However, if you're really serious about photography, to me the three features you want in any digital camera (superzoom or otherwise) that you should look for, in order of importance are: 1) full Manual mode (to take control of the exposure explicitly through aperture or shutter speed settings), 2) RAW capability (for the most latitude for post-processing edits), and 3) a flash hotshoe (so you can do off-camera lighting if you so desire).
Neither of those cameras has RAW or a flash hotshoe, so personally, I wouldn't contemplate getting either one (although I suppose a flash hotshoe could be optional for a lot of folks). If you look at a camera's specs, they'll tell you if the camera can do RAW, and looking at the top plate of the camera will show you whether or not there's a flash hotshoe.