I have a 13.0sb and it is VERY similar in size/displacement to my buddy's 143D.
A 13D will be a smaller boat than a 13.0SB. A 14.0SB will be much bigger than a 13D.
The Tribs are a lot more similar to the R series.
Decide whether you want the round profile or the diminishing tubes. If you like the round profile, decide if you want the more inexpensive boat or the 10-year warranty and USA made. To me, one of the biggest benefits of the R and D series is that you can get the Sealed Pocket Floor, which makes your raft a lot more nimble..with the Tribs, you only get the water-filled open floor pocket.
13 vs 14. How many people? Dogs? How much beer, exactly?
I like my 13.0. It's awesome for daytrips on III+ with my wife and kids. It gets small quickly when the rivers get big. I've flipped it several times on the Lochsa over 14k, and once on the Alberton Gorge (III+) at 20k. It's fun when the rivers drop and the 15.5' raft is boring. At the same time, I have considered trading it for a 14.0. I have a couple of friends who run them on the Lochsa, and it's noticeably more stable when the river is running good...but I don't think it would be "boring" on lower flows.
Bigger tubes, more length = more capacity with a shallower draft. If you're concerned about dragging in the late summer, 14' will actually float higher.
If you're concerned about width, there isn't much difference.