The SL1200G has an extremely well designed plinth, platter, motor and motor drive. The job of the plinth is to couple the motor mount and the base of the tonearm as tightly as possible (which is why pod-mounted tonearms are problematic) while also being as acoustically 'dead' as possible.
The SL1200G plinth is a two part metal system; the two bits (the top and the subchassis, bonded together) rob energy from each other since they have very different resonant points, while allowing for very good coupling. Two damping systems are then applied to the plinth, which form the base of the machine.
That's the mechanical engineering needed to control air-born or induced vibration from influencing the sound, since any vibration that actually gets into the plinth is in the same plane in at the base of the motor and the base of the arm.
The patter uses a similar technique of bonded dissimilar metals to create anti-resonance. It is then also damped. So it need not be super high mass to be low in coloration.
These two things really aren't well understood about this design. Its far more advanced and far less resonant than 99% of turntables ever made. Its actually got a better plinth than any of the SP models, which really don't have a plinth at all since they were designed for radio station service. So the motor mount/tonearm mount coupling is actually superior.
The weaknesses of the machine are two fold. The platter pad is their traditional fare, which is a joke. The platter pad's job is to simultaneously damp the vinyl during playback as well as the platter. If this is not done correctly the vinyl will 'talk back' to the stylus and so introduce distortion/coloration. The best commercial pad I've seen so far for this is the Oracle mat, which has to be permanently adhered to the platter. This means the platter mount screws probably should not be installed. A complication is the record spindle really isn't long enough so you can only use a record weight but not a clamp. I expect to fix this on my machine this winter. The stock platter pad is one reason I think you see so much variable results people talk about; the job of the platter pad is IMO poorly understood in the marketplace.
The other weakness is the tonearm, which by high end standards is actually quite good. But there are better arms and if a proper arm board is fabricated (of the same material as the plinth, otherwise colorations are introduced) better arms can be installed. I've installed the Triplanar arm, even the 12" version with excellent results.
IMO these two things are needed for the SL1200G to be world class by any metric.
So can it challenge the state of the art? Yes- easily. Most machines are less resistant to vibration due to poor plinth design and most do not have effective platter pads (which is an easy fix in most cases). I know it hurts a bit when so many high end turntables are far more expensive; look at it this way: Technics has a far greater budget for proper R&D and the manufacturing ability to make the machine in quantity. A smaller manufacturer, if they were able to engineer the motor and its controller, would be charging several times more to build the same thing. So you should not let the lower price fool you into thinking it has less value. IMO/IME it has more.
