Talk about a wide spectrum of vehicles! Chrysler is by far the low end of the spectrum. The Sebring convertible is not a horrible vehicle, but the Chryslers have had build quality issues for enough years that I couldn't warrant getting one, even if it was 7 years newer than the Saab.
The Saab is more of a entry level luxury car. In '96, the company was not yet fully owned by GM as it now is (but not for long thankfully), so the design you will be looking at will have less GM influence than the vehicles on the road today. Regardless of whether the Saab was built under GM or when Saab was part of Saab-Scania, it is a vehicle that far outpaces the likes of a Chrysler Sebring.
Given the seven year difference, there may be some additional safety feature implemented on the Chrysler, but Saabs are extremely safe vehicle to begin with. The one item to make sure of it that the Saab underwent regularly schedule oil changes. They have a history of sludged engine problems if the people who own the car don't keep up with regular maintenance.
Of course Mercedes is in another class really. For a comparable convertible, you should have a car with excellent fit and finish, but it will cost you, both at the time of purchase and as things go wrong with it.
Personally I'd go with the Saab. Its a good balance of safety, sportiness, and comfort. It basically shoots the gap between a Chrysler and Merc, regardless of how large that gap is.