I'd say they're so similar not just because of conversion issues, but because the only real differentiation between them is what the mapgen prefers to seed on each planet. List 5 differences between metal nodes and crystal nodes. One provides metal, one provides crystal, but that's about it. Sometimes the map decides to have more metal, or more crystal, on a given planet. Nothing's limited, they don't really feel different in where they appear, nothing. In Starcraft, Gas comes from geysers (and you need a refinery for it), while minerals are just in the ground. In Supreme Commander, you can only get Mass from specific nodes, while you can generate energy from literally anywhere you can build a reactor at. In AI War, metal harvesters can only be built at particular nodes, and crystal harvesters can only be built at its particular nodes. They pretty much just feel the same. If crystal were actually different outside of just the name of the harvester that got it, I'd more entertain the idea of keeping them separate. That, unfortunately, is a lot more complex than just removing conversion or anything.