My approach for this too-common situation is to start off with "either one is fine for me" or something similar, and if this isn't acceptable for the requestor to list the pros and cons I see in each option.
"I like this one because of A and B, but it also X and Y which aren't ideal because of Z. The other one is good because of J and K, but it also W and X. Either one will work - which do you prefer?"
For people I trust (and it's usually only these people for whom I'll put in the effort) this usually gets the conversation going in a more positive direction. Me sharing my personal pros and cons often helps them articulate their own, and that can help them make up their own damned mind.