Well, the obvious answer is ride my Audax on June 7th! I'd recommend the 200 - it's quite hilly, but not visciously so.
A week's taper will be fine if that 180km is well within your abilities (which it sounds like it is), and you take it easy.
Lastly, your final question; both events require 95% the same kind of training, so just choose on which event you will enjoy / find satisfying.
(Personally, having travelled all that way, I'd want the most cycling I can get.)