Tango Down are easily the fattest of all of them, well, maybe the Dark Parts ones someone just mentioned are fatter. So I dont like to use all Tango Down rails if Im not using a vert grip. It just makes the forend too fat and bulky. If I am using a vert grip, then the Tango Downs are great. They are easily the most durable of all the pannels available.
The Magpul XT pannels feel the best to me. They arent hard and have great texture. Rich should incorporate the texture from the MIAD grips into the XT pannels (with all the little magpul logos). These pannels can have a tendency to get a little loose or wobbly on the rail though.
The ladder pannels offer the least rail protection, but are very comfortable and low profile. They stay put as well. I've yet to see one get loose or come off. In fact, I know a few people who have had a hard time getting them off with just their fingers once installed.