This is too open-ended a question for anyone to give a definitive answer, but it all boils down to one thing anyway: buy the camera you feel comfortable with. Go to a store that sells professional gear, and have a salesman show you the features of the different models. Get them in your hands and use them. You'll be using this thing daily for a long time, so you want something you find intuitive. When the action is fast and furious you don't have time to stop and look at the dials to change settings.(posted 9175 days ago)I had the same question in 1985. I found an excellent store in San Antonio, and the choice came down to a Nikon F3 or Canon F1. I went with the Canon because I found it much easier to remove the lenses. A couple of my friends bought into the Nikon system, and a couple others bought Canon systems around the same time. We all used our cameras productively for 10 years or more, and we all got excellent results. None of us had problems with our sytems. We even traded gear a few times, just for grins, and still got excellent photos.
Canon, with the USM lenses, seems to have a bit of an edge over Nikon. Nikon's viewfinders are better. You can't lose with either system. What do I own, you ask? None of the above. I use an assortment of old medium format TLRs for landscape work. Yesterday I bought a used Minolta Maxxum 700 with 50mm macro lens for my son to use this summer as he travels the country with his grandparents.
Stick with one of the major brands (Canon, Minolta, Nikon, Pentax) and you'll get a good system. Canon and Nikon have the best lens selections, which is a major consideration for someone as serious as you. However, if Minolta and Pentax make all the lenses you want, and you like the bodies more than Canon or Nikon, go for it.
You might also want to think about getting a used medium format TLR in addition to your 35mm gear. They are wonderful within their limitations. They don't have interchangeable lenses (except for the Mamiya C series), and you aren't going to shoot sports or macros with them. However, they are great for landscape work. Light, reliable, and the extra negative size makes a world of difference.