Joe....easy to answer. The longest lasting system is going to be primer and paint.
Scrape/sand/clean all areas to be painted. If more than 40% of the old finish comes off after this - prime everything. If less than 40% spot prime will suffice.
I would prime with a good exterior oil primer - I am not an old guy - a long time in the paint business though - and I just like oil primers on wood.
After that is dry - 2 coats (never just go with one coat outside) of top quality 100% acrylic latex paint.
Two great products I know of are sold at ICI Paint Stores.
Glidden Ultra-Hide Exterior Alkyd Primer
Dulux Ultra or Dulux Fortis Exterior 100% Acrylic Latex house paint.
Both are great products - and properly applied - will last a good long time on a windy hill in New England!