HeartGold is my preference I got Gold when I was younger. What did you have when you were younger?
It all really depends on what pokemon you want forget about ho-oh and lugia you cant get them in both games think about version exclusives like in heart gold you can get kyogre and groudon in soul silver personally for me i like heart gold because that way you can get lugia at a much higher level and you can finish the ruins of aplhs alot quicker