The thing I would recommend most strongly is finding somewhere you can actually try each of these hands on. Unless you are planning on becoming a professional photographer, both of those cameras will work just fine as will the current offerings from Canon, Olympus, Pentax, etc.. But whether you find the user interface a particular brand uses will work best for you is an intensely personal thing. We have a bunch of Nikons at work and I personally find the interface annoying but they are the top choice for many of the people in the office.
Bring a memory card to the store and take a few pictures with each. Wander through the buttons on the back and the menu structure and see how difficult it is for you to use the functions you would use most often such as reviewing photos, zooming in on them, changing the exposure compensation, changing the ISO and white balance, etc..
Once you have found the user interface that works for you, then you can start thinking about what different features, lenses, etc. you need for the particular type of photography you do. Do you take a lot of low light photographs? Then that Nikon might be particularly useful since it goes up to a pretty high ISO while keeping noise fairly low. Do you have specialized things like birds or tiny objects that you photograph? You might want to consider carefully since the really long lenses in Nikon's line (and Canon) are super expensive. Some of the second tier brands like Sony, Pentax and Olympus might have somewhat lower prices. Do you like using classic lenses? Current Nikons can use any Nikon lens going back to the 50's. I think Sony's can use old Minolta lenses but you should check if that is what you want to do.
Taking shaving one day at a time.