Yamaha GT 2000 vs new SL Need advice.

What gives us audiophilia nervosa.  Have you located a GT2000 in Japan that is for sale?  One good thing in your favor is that the reputable Japanese dealers, either when you go there in person or on eBay, tend to be honest in representing their products. 

Paradoxical to the situation in the USA regarding GT2000s, they are all over the place in Tokyo.  It was evidently a very successful model for Yamaha, back in the day, in that market.  It's much easier to find a GT2000 in Tokyo than to find an SP10, even.  Try "Hifido English", on line.  They very often have a nice one for sale which they will pack and ship to you. And don't buy any of the lesser models; the GT2000 or GT2000L is the way to go.

I’ve only owned the Mk2, and I’ve compared it on the same system to a Mk3 and a Denon DP80. To my ears, the Mk3 was a very clear winner vs the other two, and the DP80 nosed out the SP10 MK2. I’ve since acquired experience with two more DD’s, These use coreless motors, the L07D and the TT101. In this respect and in others related to the design goals of their servo systems, platter mass, plinth, etc, these two are different from the first 3 I mention. The L07D and the TT101 seem to challenge the MK3, but they are not better. However, I would and do take either over the DP80 and the MK2. Therefore, I am tending to favor coreless motors, all other things being nearly equal. (The Mk3 has other features that raise up its performance uber alles.) On this basis, I would guess that SL1200G might outperform SP10 Mk2 but not necessarily the GT2000 (1200G and GT2000 do have coreless motors); I would want to audition that comparison for myself.

The GT2000 has already lasted ~30 years. Why would it not last another 30 years with proper care and use? Perhaps the bearing will need attention eventually, if it doesn’t already need it, but otherwise....
I do advocate going through the GT2000 thoroughly from the outset, with new electrolytic capacitors, possibly upgrading transistors, calibration of the drive system, attention to the bearing, etc. I am only guessing that this would still be way cheaper than purchasing a new SL. The great revelation of this thread is that in fact we are NOT living dangerously with vintage direct-drive turntables.

The OP’s question is about choosing between one DD and another DD, whereas you made a paradigm shift by going from a suspended belt-drive to a non-suspended idler-drive. Good choice, by the way.

EDIT. In my remark about not living dangerously, I was thinking of the other thread on direct drive, the "living dangerously" thread. Sorry.

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.