Scooty, I Would keep the D1200 vs. the '94 S3. Of course, it comes down to individual preference. But, both are variations on the initial T3 lineup. In those years Triumph used modular construction and there is not as much difference as you might think among models pre 1997. The exception is the mighty Daytona 1200 motor (the Trophy 1200 was in a de-tuned state for touring).
You would be trading horsepower and torque for less weight and marginally better handling. Also, no fairing if that is a factor. The D1200 is relatively rare and a blast to drive at speed. It's just a big, fast and heavy locomotive of a bike. If you love your D1200 you may be somewhat disappointed by a '94 S3.
The tougher choice would be between the D1200 and either the 955 S3 or the new 1050 S3. The newer triples make more power than the old 885 and the frames and suspensions are much updated and improved as well.
Choose wisely and ride safe my friend!