I've not had the implant but I was on the Depo Provera injection, you have it every 3 months and over time most people stop having periods. I initially went on it because of painful periods and it worked wonders. I had to come off it last year as I started having random periods again so they thought it might not be working properly any more (I'd been on it about 4 years, and a few years in the past).
I've now got the Mirena Coil, unfortunately it hasn't stopped my periods completely (most people stop), though they are shorter and lighter than normal. I would have had the impant but they said if the injection was beginning to cause trouble, the implant might too. One really good thing about the Mirena Coil is that it last for 5 years, so you don't need to worry about it.