I do both, but have you ever written 3-4 pages by hand in one sitting? I've got exceptionally strong and flexible hand and finger muscles, but even I have to take breaks and shake out the lactic acid build up. Alcohol only helps so much. A manual typewriter can take its own toll, but it's different. Pen and paper are very portable. Manual typewriters are portable and efficient.
My IBM Selectric III is not portable but that monster can bash out words so fast and with audacity that I'm glad it's an option. Granted, I bought two Selectrics before (a I and II) and both died due to being worn out and gross, but for $50 and in mint condition, I've enjoyed it immensely.