The way that Sean puts it here, I would have to agree with him, and not Brad (sorry Brad).
I think Sean is saying that technology is not the same as capitalism, or not the same as whichever mode of production under which it comes into existence. And that's right. There is nothing intrinsically capitalist about the computer or the laser, it just happens that they were developed in the era we call capitalism, when human relations were ordered according to the profit motive.
As to the cause, it is not really right to say that capitalism _causes_ the inventions to happen. Seeing science and technology as just special instances of labour under capitalism it would be more true to say that labour is the real cause, and capital only its subordination to private interests.
In the case of agricultural productivity, the two most important technological advances in the twentieth century were synthetic fertilisers and motorisation. Empirically, it seems undeniable to me that these two are central to the increased output that meets the increased demand of 6.6 billion mouths. But neither are intrinsically capitalist, it just happens that they were developed and distributed under (mostly) capitalist social relations.
I support the technology, not the mode of production, which has exacted terrible costs, just as it has permitted some technological advance.