Delonte West is not the Cavs' best defender, not even their best perimeter defender. LeBron is the Cavs best defender. And while Delonte West is a pretty good defender, it's well do ented that he'll struggle against bigger, more physical guards. The Cavs have two other guys that may or may not be better overall defenders but match-up better against bigger guards in Anthony Parker and Jamario Moon. Additionally, they have been playing Jawad Williams at the 2-guard some as well and he's tall and long for a guard with good mobility.
The Cavs actually have a lot of defensive options to throw at Jordan and Pippen. The Cavs also have Shaq when healthy, albeit older and nowhere near as dominant as he used to be. He can still be a mismatch and a problem, and sometimes games can be decided by one or two possessions. I think healthy, Shaq would be a guy that would help these Cavs against those Bulls.
On paper, there's actually something to the comparison. But you could do the same with the Lakers against those Bulls. On paper, it looks like a fairly even match-up. But as cliche as it is, the games aren't played on paper. There was something about those Jordan Bulls teams that went beyond talent. There were arguably more talented teams they faced (although I do argue that Jordan's compe ion wasn't all that great during his run, especially compared to the 80s championship compe ion of the Lakers, Celtics, Sixers, Rockets) at least when it came down to depth and balance of talent. After Jordan and Pippen, the talent level dropped significantly. But those role players on those Bulls teams knew their role and limitations almost perfectly and rarely if ever went beyond them. You look at coaching and those Bulls teams were stronger, more efficient, and executed better at both ends of the floor. And the ultimate trump card of Jordan's will to win. It trumps anything that can be put on paper. As talented as LeBron is, and you could argue he's bigger, stronger, faster than Jordan, there's only little evidence that shows LeBron can will his team to a championship. His game 5 in the 2007 ECF against the Pistons 25 straight point barrage is an example of him willing his team to win. But can he do it consistently and enough times and against the best teams in the league for his team to win a championship? It's an intangible that can't be quantified or qualified and for the purposes of this comparison with the 91 Bulls is probably the distinction that until proven will give the edge to the 91 Bulls.