Doggus,
Well, I don't have much useful information for you. We bought a Cannondale last year and I've only even ridden one other tandem and that was 30 years ago. I don't know what the Cannondale weighs but it is built like a truck compared to my other bikes. The shifting is as good as any bike I have (I've got a very good race type road bike and high end mountain bike). The handling sucks (sloooowwwww) and the frame isn't very stiff, at least compared to my road bike. The ride is very good, especially compared to my road bike. We ride it just about everyday towing about 80 lbs of trailer. Working on it is like working on any other bike, just a little more stuff there with a little more interdependency.
The other tandem is one we got on the farm when I was a teenager about 30 years ago. It was a Schwinn, 5 speed, full fenders, drum brake, big tires. That Schwinn with me and my brother on it never lost a race, it had a screaming top end! I don't remember it weighing much either. We had a-lot of great times with that bike. The slingshot equipped stoker solved many a dog problem too.
Get the bike you can afford. From what I'm seeing here all of these bikes are very good. It's what you do with the bike you get that matters.