i took cerelle (and its counterparts with different names) for a couple of years, and have not got the implant. As others have said its a safe pill and much safer (in terms of the risk of blood clots) than the other type of pill. Yes you can have irregular bleeding, constant bleeding, or even no bleeding (mine have gotten more irregular), it's likely not going to be that bad, and worst case you can just stop taking it (and use other protection).
the implant actually uses the same hormone as cerelle, so the effects will be much the same with both of them, except the implant is harder to remove.