Well the starting 5 of the 86 team I believe was a little more in their prime Bird 29, McHale 28, Parish 32, DJ 31, Ainge 26, than this year's starting 5. That helps immeasurably all playing together. Rondo is still prone to young mistakes and not always aggressive, Perk hasn't hit his peak yet, and KG hasn't really been the old KG. Also I agree that the KG I see now would have a tough time with McHale, Pierce would have a tough time with Bird (that would be the matchup I would love to see on both ends of the court), and as good as Perkins is defensively now he would still have a tough time with Parish, and even Rondo would have a tough time with the bigger DJ.
However we are only 12 games into the season and don't know what the finished product will look like and what trades Ainge makes, how well KG will return to old form, how much improvement Rondo and Perk make throughout the season, and so on.
I think the only advantage we have other than what someone else said Ray over Ainge is that I believe the end of our bench is more talented than the 86 team. That doesn't really mean anything though since those players hardly play.