Stephen King said, “By the time I was fourteen the nail in my wall would no longer support the weight of the rejection slips impaled upon it. I replaced the nail with a spike and went on writing.”
I think this is the soul of a writer. We're going to get rejections, we're going to find people who don't like our work or suggest we not even publish it. Does that mean we should avoid negative feedback? If it is constructive, no way. If it is mean and hurtful, in a malicious sort of way? yes, get away from it. So, in light of this I would suggest giving the reviews, don't pull your punches, but if you can give specifics without being malicious I say give all you can. As an author, that is what I would want to know.