Organic Technology: It does exist in the universe (see, for example, the Gardeners of Rechesh we mentioned back in Flesh Versus Steel and the qucequql, who went an organic-technology route due to their underwater origin, or for Imperial examples, the bioengineering esseli, and the colonists of the planet Kythera (Imperial Core)).
However, while there exist organic fundamentalists (the aforementioned Gardeners of Rechesh), they are crippled by the disadvantages of their technology. Organic structures just plain aren’t that good at a great many tasks, including handling high energies, radiation, etc., etc., and very often, the things that they are good at are different from their inorganic equivalents. A cortexture is a perfectly good organic neural-net computer built out of actual neurons, but it would be wasted performing the same tasks as a regular inorganic processor, or quantum processor less efficiently when it can do the jobs suited for neural-net processing more efficiently. The right tool for the right job, say sensible users…
…such as the esseli and the Kytherans – and the qucequql – who are a more logical lot, and are more than happy to use organic technology where it makes sense, and wrap it up in a nice neosteel hull with a perfectly inorganic fusion reactor the rest of the time. Or engage in bionanotech games with materials and devices that couldn’t strictly be said to be one thing or t’other.
Living Starship: The genesplicing esseli and the residents of Kythera – the Empire’s masters of biotech – are the chief users of this sort of technology in the Imperial context, although they’re by no means the only ones in the Associated Worlds to go for this sort of thing. Although, in deference to certain realities about the capabilities of carbon-based organics vis-à-vis metal and ceramic, the hulls (mostly, although some specially-engineered and composite-laced wood-analogues are an exception), engines, and other high-energy components tend to be not living in anything resembling the conventional sense; i.e., the ships are only semi-organic. (See also, for example, the note under Flesh Versus Steel about the Gardeners of Rechesh; while they do manage to construct entirely biotech spacecraft, their hulls are vulnerable and engines slow compared to virtually anything else anyone’s ever put into space.)
Flesh Versus Steel: Both have their partisans within the Eldraeverse – many branches of the Silicate Tree are steel fundamentalists, although how much of that is rationalized hatred of their organic creator-enslavers is open to question, and they’re not the only ones. Likewise, there are partisans of the purity of the flesh, like the purist Gardeners of Rechesh (who have endless trouble trying to build organic-tech spacecraft, etc.) and more moderate, tool-accepting groups.
The Imperials, contrariwise, would point out that choosing one above the other is to pointlessly limit yourself. Of course, since the average Imperial is wandering around with plenty of “steel” (in the form of billions of technocytes and technosomes, etc.) scattered all through their “flesh”, they would say that, now wouldn’t they?