I prefer not to go to PMs, as I believe this topic is a public one, that is relative to the thread, as it affects the choice someone might make of a component in their conversion. Of course you are free to not reply, if you don't mind if others disagree, however I'm giving others reasons as to why the hyd version is a better solution.
I understand that you are saying the clutch lag leaves the gearbox under some load while the gears are being changed, which leads to wear, and then failure.
By the time the slack is noticable enough for the user to tell, and to adjust it, it's already far worse than a self adjusting system, thus allowing the drive to be putting more strain on the box over longer periods during gear changes, which is what I was saying, and what you were saying the apparent lag in a hydraulic system does. I do concede that a cable system could self adjust though, but I've never heard of, nor seen one, mainly because they haven't been used here for about 20 years, except in motorcycles, where you hardly need to use the clutch to shift anyway.
Back to the point about the best or cheapest method for the auto industry, that is my point, they would most likely use the cheapest if there was no other significant advantage to using one over the other, but a hydraulic system, with seals, pistons and fluid, is going to be more expensive, yet all current production cars here use hydraulic. And if you think using the best tech in the auto industry is "not all that important" then don't tell that to our auto makers, they make us cars with aluminium cylinder heads with double overhead cams, variable valve timing, sequential electronic fuel injection, turbos, air conditioning, in dash cd stacker, radial tyres, alloy wheels, disc brakes, independant rear suspension, etc, etc. (And that's only one family sedan, add the turbo for the sporty version.)
And what DOT standard does the clutch disengagement mechanism have to meet? Here the standards are for safety and emissions. The government couldn't give a crap whether your car doesn't work half the time, as long as it is safe and doesn't grossly pollute.
I wasn't talking about the brake systems that drag racing teams use, I was talking about racing in which brakes are actually used IN the race (not where it is made as light as the rules will allow), circuit racing, where it would be imperative to get the best response from them at every corner, lap after lap.
Overall I don't think any lag of either system is substantial enough to warrant the other being the definite choice, for any intended use, but there are other factors that deem hydraulic to be better overall, such as effort, hose VS cable routing, and cable sticking. I especially don't agree that if you race with a hydraulic clutch that you will break your gearbox BECAUSE of the hydraulic clutch.