I would say that it depends on the angle.
For someone, who is a believer, prayer can be a way to say all the things you realized had gone unsaid until it was too late. It can be a way to talk out your laments that might otherwise be bottled up inside you. (very unhealthy)
It gives you an audience with your god and lets that god carry much of the burden.
If you are referring to the prayers of others I would say that it helps them far more than it helps the one being prayed for.
Of course if you aren't a believer it is pointless either way.
As someone who once worked in a cemetery and saw a lot of grieving it seemed to me that those who were too religious kept the wound open far longer, therefore prolonging the pain.
I will offer this observation The people who had closed casket services were far better off than those who had open caskets. If you hold, as your last image, that person as they were in life you will feel much better than those who's last image is of a corpse in a box. I have seen a lot of dead bodies and not one of them looked like they were peacefully sleeping.