Loren Woods is a better option the Justin Williams.
I don't think the two are relevant yet.
Williams isn't really an NBA center yet, unless we go small. Williams is 6'9" 220-225 (last we know), have even seen him being at 210-215. It's one of those ranges anyways, and he would probably need to add some mass to his frame to be the back-up center or a regular-playing center. We don't know what he's doing this off-season, but I'd assume he'll have some added mass to his upper body. Which his frame suggests he can.
Aside from all that, he's likely to be a third big man on the team if he makes it. Back-up center? That's a stretch right now, and really uncertain in general. The roster situation has to be more clear and situated before that can be discussed legitimately. Which I would think would come around in October. Considering there is all this month left, plus just about all of September for stuff to be done with the roster.
But, if I had to choose between one of them for a spot on the roster, I'd take Williams. I feel he's gonna be a solid big man at least in the league, and think he'll ultimately be better than Loren Woods.
If it's a roster spot Woods will be fighting for in camp? That still isn't quite clear. Two reports so far suggest Woods is getting a one-year guaranteed money deal. While Grant thinks or says Woods deal is a non-guaranteed deal.
So, the reports are indeed conflicting, I'll take the aforementioned two reports over Grant.