Before declining to offer an opinion, it's worth considering whether you'd benefit from the decision being made. (For instance, you could get a prompt dinner.) If so, why not offer a little help? Decision making can be tiring work, and any input can make it easier.

You could: - mention any limiting factors (i.e. I have $20 or 1 hour) - Mention options that are convenient - Offer support to the person who makes the decision (particularly if you can avoid critiquing their choice).