I know this thread is a little old but I happened to come across it and can provide some input.
I have experimented with lots of antennas with my portable HF radio. It all depends on what you want to do. Buddipole and Buddistick antennas are nice and modular but somewhat heavy. End fed half wave dipoles from Par Electronics are light and only need one support, just throw it up over a tree branch and get on the air. I would highly recommend the EF-10-20-40 for the FT-817. It is compact, light, multiband, and works great.