I started with a seat harness and switched after a while to a waist harness.
I never used a chest harness, so I don't know the difference.
You should try the waist too, to know what is best for you, since everyone has different opinions.
Others tell me, that they can't use a waist harness. I tried to use one time my seat harness again, but couldn't ride with it at all! So I stay with my waist harness, since it is more comfortable for me, when I pull the bar towards me than pulling it down to my ....