I can’t really speak to the other tandems but the Cannondale isn’t a large/small. It’s a large/medium. I have a large/small Cannondale and the difference is far larger than the bike you are showing. Mine’s a 58cm front and a 44 rear. The one you are looking at is more like a 58/49 front/rear. My wife and I have ridden that size but it never really fit her 5’ frame all that well. The Cannondale we have now is a much closer match.
As to ride, far too much is made of how soft steel is. It isn’t. It’s stiffer than aluminum. The tubes used are a smaller diameter so they feel a little softer but an aluminum bike using the same diameter tubes is a noodle. On the other hand, we have a very old Burley Samba which is a mountain bike type tandem without bracing between the front and rear. It
is noodle. Any movement by my wife causes the bike to wander all over the road. It’s a bear to handle.
The Cannondale (which is new to us) is far more comfortable and handles much better. The frame isn’t all that punishing and, more importantly, my stoker can do some movement without me thinking the bike is going to go left instead of straight.