No idea if it's good or bad, only time will tell but personally, I don't see it as a really big move.
Pros: Williams not doing well so he can prove himself as a driver (if they get more points with him, it's kinda proof right?
Cons: How far more can Sainz go with Williams?
I can't put my finger on it either, I think Sainz is better than the Williams, but it was probably his only chance to stay in Formula 1, if you sit out a year it can happen that you don't get a seat at all, at Williams he just has to score one or two points to get back into a better team.
