Detroit wouldn't beat Cleveland regardless, they lost their winning edge after their championship run and they turn on their coach the first chance they get. They're whiners.
San Antonio doesn't scare me nearly as much as Detroit did as a Cavs fan,
San Antonio doesn't have the defensive presence the same way Detroit did. 
Floppers like Ginobli don't scare anybody the way that guys like Prince and Wallace can with their ability to block shots. Duncan obviously is probably the biggest presence in the league in the paint, however he is only one guy and Lebron will take him to school one on one when he makes his move to the basket. The only reason Detroit had any success defending Lebron at all was because they attacked him with numbers.
Detroit had some height across the board to combat Cleveland's size with, San Antonio doesn't have anything close to that. It doesn't matter what all these "experts" are saying, they just don't want to be the guy who steps out on a limb and picks the Cavs (San Antonio is the safe pick). It's matchups that make ballgames and Cleveland matches up much better against San Antonio than they do against Detroit, plain and simple. Cavs will control this series.