TP HD for a number of reasons.
SS is too new to be remade anytime soon. While it would look absolutely gorgeous in HD, it already does look gorgeous. I have some personal gripes with SS and I believe that my problems with the game couldn't be fixed in a remake for they are too large of problems. I think an SS remake would be a big waste of Nintendo's time.
Now TP on the other hand was restricted by the technology of its day. If that realistic/dark approach were to be remade into HD there is no telling how awesome it would look. Plus, I believe TP only had small issues (ex: bosses aren't hard, field enemies are morons, Hyrule field is a bit barren). These could be easily fixed in a remake with maybe a Hero mode like in SS and now WWHD, the bosses could be made quicker and maybe a few new attacks thrown in, and they could always pack a few more secrets into Hyrule field