1) comparisons by mass of silk produced as a percentage weight are irrelevant. (at any rate silkworms win that one hands down: cocoons are almost half of the weight of the worm + cocoon. Silk protein produced in bacteria is far less than half the weight (low single digits percent would be the usual) But all that matters is the realtive costs.
2) bacterial production facilities are expensive and high tech, more so than low tech silkworm farms. Round 1: silkworms.
3) extraction of spider silk protein from bacterial production will be a very complex and expensive process. Reeling and spinning of silk will, at least in the beginning, involve considerable labor (although low tech and can easily be located in low wage areas that need the work) Round 2: I'd give it to KBLB but opinions may differ, call it a draw.
4) Mechanical spinning has not been achieved yet. AmSilk's current silk is only 45% the strength of spiders (barely over half of KBLB's 80% in Monster Silk). IN ADDITION, AmSilk said of its mechanical spinning:
And that's for a pathetic 45%, only barely better than SILKWORM silk (Nexia went bankrupt with a 40% silk!)
Round 3: KNOCKOUT by KBLB!
Just to drive it home: Mechanical spinning would require a LOT of custom built very high tech equipment. High tech is expensive. CUSTOM high tech is mind bogglingly expensive. Just to understand the precise hydrodynamics of the turbulent flow in the microtubules and how it affects the salt concentration AND the pH AND MOST IMPORTANTLY their rates of change RELATIVE TO EACH OTHER(which will be absolutely critical to get right for success) will take years of very difficult research. And those may well not be the only two important factors!
PS: If zwitterions are involved, which they may well be, then VERY PRECISE control of pH change AND it's realtionship to change in salt concentration will be very critical. This does not sound at all like a "robust" process! This is the kind of process that biological organisms, with many millions of years of evolution under their belt, do routinely but which we currently can only make very crude and limited approximations of. THIS IS THE BASIC PRINCIPLE OF KBLB (AND OF PRODUCTION IN THE TWENTY FIRST CENTURY, NO MAKE THAT THE THIRD MILLENIUM:
Mechanical production is inherently limited: Complexity can be hugely expensive and factories are very expensive and must be built in proportion to the amount produced and require masses of highly trained personnel.
Biotechnology can handle stupendous complexity with ease ("stupendous" is quite appropriate if you have any grasp of how complex a eukaryotic organism is (and that's just the very tiny fraction we know about it which is totally dwarfed by what we don't know). And the "factories" are self reproducing. And for production in animals and plants, the great majority of the workers are agricultural workers.
And, of course, biotechnology can produce a vast array of things that could never be produced mechanically or chemically.
Anyone who doesn't get that, doesn't get biotechnology.