During the course of the year I started routes in TS2010, TS12 and TANE but since moving up to the new laptop my big projects are all in TANE. I have TS12 (Steam version) installed as a backup but haven't got round to putting TS2010 back on. At this point, the only reason for using TS2010 would be to access the full range of assets from the product history, however... most of these are on the DLS anyway.
Now I can run TANE without totally melting the hardware, the appeal of Protrack and superelevation really trumps the earlier stuff, not to mention no more disconnections at fixed objects or having road and rail splines standing proud of the surface. Lots of assets starting to appear which are TANE only (the ST_RMM trees for one). On a more practical level, TS12 will be unsupported in a couple of months so doesn't really have a future if the DLS is the intended destination for your work.