What vintage Technics tables are best?

Agree with Corby. In late 2008 I took an SP-25 with the factory base in on trade. It sat in my storeroom until earlier this year when, for grins and giggles, I mounted a modestly priced Hadcock tonearm on it. I had no clear expectations.

For about $1000 it will smoke any VPI, Nottingham, etc. up to and perhaps exceeding $3K.

The only modification is a copper mat replacing the cheesy factory rubber mat supplied by Technics.

IMO
YMMV
Dealer disclaimer.

For mid-priced Technics, I prefer the SP-15, SL-150MK2, SL-M3 over the SL-1200Mk2 because they ALL have better platters.

For mid-priced Japanese direct-drive turntables, I prefer the JVC QL-7(TT-71) over ALL the above Technics.

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speaking if jvc, i also built a plinth for a jvc ql-5, added a black widow arm and a soundsmith cartridge. i still prefer the sp25, but that is probably the arm/cartridge combo making the difference. it's hard to compare tables since it's rarely apples to apples comparisons, there are way too many variables.
also, on the mat subject, i added a carbon fibre donut to the rubber mat on the technics. blacker backgrounds than the rubber mat alone.
the jvc is definately a nice solid table. the platter is heavier than the sp25. there's a pic of my table at:
http://www.canuckaudiomart.com/details/180794-unique_turntable_jvc_ql5_direct_drive_in_custom_plinth/

If you limit yourself to the "Technics" brand, then the SP10 MK3 is the obvious winner. It's the most expensive, rarest, and best of the Technics direct-drive turntables. However, IMO, you don't have to spend nearly that much to get very close to it. Tables that I have personally auditioned (and own) include the SP10 Mk2 and the Denon DP80. The latter is a really undervalued sleeper. I also own a Kenwood L07D, which is fantastic when electronically restored and set up, so I would imagine that its smaller brother, the KD500 is also excellent. The better vintage Pioneer direct-drive turntables are also excellent and plentiful in the US market. Oh, and mind what Audiofeil said, the mat makes a huge difference on any of these turntables. I use a vintage SAEC ss300 metal mat, and it kicks butt over the stock rubber mats on any of the aforementioned. In choosing an aftermarket mat, stay fairly close to the weight of the stock rubber mat you are replacing (within 0.5X to 2X in weight, for example). The servo mechanisms were optimized for a specific mass of platter + mat. One cool thing about the L07D is that by flipping a switch on the outboard PS, it can accommodate additional peripheral platter mass, a ring designed and implemented 30 years ago.

I own a Technics SP-25 with stock base, and although the mat is poor, the turntable seems to hold up to the SP-10 mkII well. It clobbers the 1200 series and can be bought used for much less.