Another vote for the beanbag mount. It gives you some flexibility to move side to side and to take it down easily if needed.
What I really like is only having to move my eyes down to a spot ABOVE the dash rather than below where the factory units are. There is a HUGE difference between glancing down to above the dash versus down below the dash.
I've used both extensively and would never go back. As for windshield mounts it seems most have far too short of "arms" and you can't reach them. I saw one in a passing car recently that was much longer so they are out there. That would seem to be the best solution so you have the ability to move it around so much. I'd guess the arm was 8" or more.