I have a Precip, but I no longer use it for backpacking, strictly because of the weight.
The Precip has huge pitzips, and the pockets are made of mesh, which create there own ventilation as well. Neither of these jackets fabrics expel moisture very well, so you will be depending on the jackets openings(pitzips) for most of your breathabilitly.
If I had to choose between the 2, I would take the Virga for the weight savings.
You should consider some other jackets like Outdoor Research Zealot, TNF Diad, or Integral Designs eVent Jacket.
Check out this article on Lightweight Rainwear, a couple years old, but very helpful.