I had a 99 Air Nautique for 3 years until about May of last year when I sold it. That boat was 100% solid while I owned it. The wake is better on the Super Airs for wakeboaring, but with enough weight you can get a very good wake. Surfing is also possible, but the cabin will have a lot of sacs. Search my name (chexi) on Planetnautique.com. I still miss that boat.
The 99 is better than the 98 in my opinion because the bow layout is better. That is the only difference. Try to find one with a 2nd gen flight control tower instead of the first one, which is harder to fold and had problems with its welds breaking.