The obvious downside in such cases is that asking for and being told what the downsides are and then ignoring them is often perceived as even worse than not asking at all.

Do you think this is true even if one made it clear that one is not seeking a consensus but reserving the right to make the final cost/benefit judgement? If so, it's contrary to my expectations (i.e., I don't see why that would be perceived as being worse than not asking at all), and I would appreciate any further explanations you might have.