[MattII]

Actually, a better analogy would be the fact that in 1900 cars were powered by batteries or steam as often as petrol.

In a more general sense, he'd like to see a tech-tree where there are, in some cases, two or more competing technologies covering a single area (propulsion for example could be provided either by a fast-but-inefficient engine, or a slow-but-efficient one, or a fast-and-efficient-but-expensive-and-delicate one).