1. I said "similar", I didn't say they are the "same" player. And I have qualified what I meant: both good defenders but Williams is a better playmaker than Lee.
2. If you just remember the T-Will and Lee from college days, I can understand why you have the impression that you have. I'm going by the most recent version of the players. You said Lee's strength is shooting, not true, not anymore. Lee bricked so many shots in NJ that fans put up pages like this:
http://netsarescorching.com/2009/12/21/is-courtneys-lower-body-the-reason-for-his-slump/ As for Williams, his jumpers had improved a lot by the end of the season. Judging by Lee's struggles last season and comparing it to William's improvement, the gap has been closed. Lee is still the better shooter for sure but if Williams keep his pace he will catch up soon enough.
I present to you what is said about Williams by NBA people:
But hey, what do those guys know, right?
As for the claim that Williams wasn't very good:
If Courtney Lee has ever averaged 14/6/5 in any 17 game stretch, I'd like to know about it; because it has never happened.