You are doing exactly what you are supposed to do - viewing your choices during the day and at night. Also make sure you look at your choices on a sunny day and a cloudy day. Next, determine whether your window covering is going to be "up" most of the time or "down". Then choose the window covering that will look best in the position it will spend the most time in.
Hope that makes sense to you.

Thank you for the recommendation. I've had samples taped up for a week so I've viewed them in all light conditions so far. I love your suggestion on deciding when they'll be down most of the time....which will be when it is sunny so it makes the most sense to choose the one I like best in the sun. I appreciate you taking the time to answer!

jillpei - best of luck!