I have ran the standard Kuiu Guide vest the last two years, and it is one of my favorite pieces. It cuts wind, shrugs off moisture, adds a bit of warmth, and layers easy.
I've used both and I don't think there is a definitive choice here. The Jetstream lite cuts the wind better and I like the longer tail. They are both very good vests, but the chest pockets are useless on either if you use a bino harness. Look at the Jetstream lite jacket for properly placed chest pockets.
If your looking for a warm vest, I would really look at KUIU new super down vest. I used the Super down jacket this year and let me tell you it is worth its price and warmth. I'm looking at getting the pants to throw on when I'm setting and glassing in wind chills days. But you cant go wrong with both companies.
The website is advertising the vest as wind proof and I know my 1/4 zip is not wind proof. I am glad that I have the SD hoodie on the way before you guys cancelled the hoodie.