Why not be tactful unless it's a serious matter. Someone buys something, a car, a dress, and shows or tells you about it, especially folks that might be somewhat less well off as yourself. Should you tell the guy that what he bought is a sh--box and you wouldn't want it even if it was given to you. Happened to me, years ago. The car was as I described but he was proud of it and had stopped by to show it to me. I dug up a few complimentary points regarding the car and I thought that was the better choice to make. Didn't cost me anything and he left feeling good about his "new" car.
Same could be said about many things. Would anyone be proud to tell their neighbor or relative that, after hearing their daughter sing during a school play, that she couldn't carry a note if you gave her a bucket to carry it in?? I think not.
When serious matters occur among friends and/or family, tact may have to take a back seat to reality but things can still be described in a less hurtful manner, unless you yourself take pride in being the "tell it like it is" type of person.