Based on specifications only, these are two very comparable turntables, both with coreless motors that I prefer.
In my opinion, if you have your GT2000 fully restored electronically and then calibrated by one of the rare breed that can do it right, you would be on the same footing with a new SL, and perhaps a few thousand dollars richer for not having purchased a new SL. One would have to do a careful A/B comparison after that, to choose one over the other. (I am not qualified to choose one over the other, as I have never heard either.) One person who can do the work for you is JP Jones of Fidelis Analog in NYC. I advise you to contact him.
In my opinion, if you have your GT2000 fully restored electronically and then calibrated by one of the rare breed that can do it right, you would be on the same footing with a new SL, and perhaps a few thousand dollars richer for not having purchased a new SL. One would have to do a careful A/B comparison after that, to choose one over the other. (I am not qualified to choose one over the other, as I have never heard either.) One person who can do the work for you is JP Jones of Fidelis Analog in NYC. I advise you to contact him.