Sometimes it's not the quantifiable benefits but the unquantifiable quality of life ones. I think really the big advantage is hard to know until you've lived in a foamed house. Not many people who have would go back if they had a choice.
That said, I do like cellulose. But I sell redefine in some circumstances where there is no hvac in the attic. If you have to count on a level of quality in attic air sealing which is not likely to be achieved by regular human beings than redefine is simply the safe approach.
I prefer to avoid recommending work that has a high likelihood of poor or mediocre results. I ask myself is the attic in question particularly likely to be a failure addressed other way?