I have a dark interior on my Plum/Black Swift, but the wide opening makes it ok. I think the Synapse would be similar. The sides zip downward fairly far so the bag interior is accessible. If the bag only opened at the top, a dark interior may make it hard to navigate. Also brightly colored and varied color contents help.
My son's Ristretto iPad has a steel interior, it has a narrower opening that is just at the top of the bag. So far it hasn't been problematic because he carries books and papers, but if he had a lot of little things inside, it would be harder to distinguish them with the darker lining.