I'd have to vote for Hamelin for pure technique; fortunately it's combined with a definite musicality. Still, at this point, his technique dominates his playing, rather than serving his art. I qualify this by saying I've only listened to the three Alkan recordings and the Godowsky-Chopin etudes, so perhaps I just haven't sampled enough Hamelin yet.
Argerich has abundant technique, and yes, I'm an admitted Argerich "fanboy," but, I think, not without reason. I understand that her rhapsodic style doesn't appeal to some, but for my personal taste, no on beats her for technique combined with the ability to produced the most amazing nuance, tonal color, and sonority. Her technique always serves her vision. That not everyone likes her vision, I understand.
Cortot was an amazing pianist. True, technique isn't the first thing I think of with Cortot, though I think he had plenty. Cortot produced consistently beautiful tone like few others have done -- maybe Kapell in his short career, and often Rubenstein -- but this is another discussion!
Topic: best technique?