Which is better, forehead implants or fat grafting?

I have little fat on my face so I'm planning on getting fat grafting, but my forehead is also sunken, so I'm planning on getting fat grafting there as well. However, I've heard that forehead fat doesn't take hold as well as other areas and falls out after a few years. I got an estimate from a plastic surgery clinic in Apgujeong, and they said that fat grafting including the forehead would cost 250, and if I were to get silicone implants and fat grafting on my forehead, they would do silicone implants (250) and fat grafting (100). I 'm having a hard time deciding which one to go with. Cost isn't a big deal, but I'm worried about forehead silicone implants because I'm getting older, and I'm worried that forehead fat grafting would fall out too quickly. Could you please advise me on what would be the right choice for my forehead?