Patents: Horizontal vs Vertical Innovation

I am a long time opponent of patents and Intellectual Property rights (to a great part because of your work), but something always bothered me and that was the ‘innovation’ argument by the patent supporters. I could always see both the sides of the arguments, yet was never sure which side is right. I can see that without patents there is no incentive to develop a technology with a large investment, on the other hand, without patents, there is probably no need of a large investment.