I believe the older Outbacks had a little better secondary stability and the newer ones have better primary but i'm not positive.
This is absolutely correct. Early Outbacks had a different bottom shape. The center of the hull was more pronounced and the outer shelves (secondary stability) could be out of the water with a light weight user.
We changed the shape several times over the years and settled on what we now have... which is VERY (Primary) stable. Now, some argue that a boat with a lot of primary stability can be a rougher ride since the boat basically sticks to the water. That means that when the sea rolls, the boat rolls with it. Some prefer to be able to balance the boat and roll into the wave which keep the cockpit more level.
Thanks for confirming Matt, i think the current design is great, i have been out in all types of conditions and i think it handles big wakes and the water in general very competently.
Once the OP has more time with his Outback i'm sure he will be very satisfied, now if he ends up with a P A and voices the same concern, it's probably hopeless.