If they are "really heavy" they have internal counterbalance weights. I have the same oars (9'6" Cataracts with magnum blades and internal counterbalance).
First, what is the measurment of your boat between oarlocks? Depending upon your boat the 9'6" may be too long, or the 9'0" may be too short. If you need the longer oars, you want the counterbalance. With 9' oars you may only want them if your boat is narrow, say with a 48" bottom and not much flair up to the oarlocks.
My Hyde runs about 75 inches at the oarlocks, and at times I wish my oars were shorter for better leverage, but most often the 9'6" is nice. the only time I don't like the counterbalance weight is when they are out of the oarlock.
Before you drop the $$ on new oars I would find someone who will lend you a pair to "test drive" in your own boat.