I have both a Haimer and a Tschorn.
I bought the Tschorn after one Haimer leaked (in the turret of my Robodrill). Fine, shit happens. Haimer's response was that I needed to wait 2 months for service, but they sell them on Amazon and were cool with me buying a whole new one (integrated taper BT30 model, so $600+) and returning the leaking one. Ok, so $600 out of pocket for a week and feeling weird about return fraud (that the manufacturer basically authorized).
That Haimer would not hold position at all. 0.002-0.004" variance in readings every time I took it in/out of the turret. My thought is that the force required to remove it from the Robodrill finger puts a load on the adjustable spindle connection in such a way as to fuck up the concentricity adjustment. I called Haimer, I got one of their VP level folks on the phone, we chatted and it was pleasant (super knowledgeable guy about the industry, so we BSd for a good hour). In the end, Haimer USA sorta leaves the 3D Taster line of business up to Germany for all service and repair. He acknowledged it sucked and the need to work on it, but my impression was that it's just not a line of business that produces the revenue to get their time/attention.
So I bought a Tschorn. Robert Tschorn is the dude who runs the company. When you email him, he responds personally. Their US distributors are pretty dedicated to the line and they either do service here, or work on an exchange basis (so if something happens, you aren't down for 6+ weeks). The Tschorn is a bit longer, but the design is a touch more robust. When functional, I don't think there is an accuracy difference between the two, but the fact that one is made by a company dedicated to the product line, where the Haimer is an afterthought to the big $$$ shrinker/balancer business sorta tells me which one I would buy if new.
