For me, 1x04 is more visually beautiful. That's the first time I sat up straighter and went "whoa! these two have chemistry!". The way she clung to him and he wouldn't let go either is just...
But 2x17 is just more special for me because they have been through so much at that point. It was more emotional and deliberate and not just accidental. They are no longer acquaintances anymore but real friends and the way Liz looked at Ressler when he told her what he had done.
She was feeling sorry for herself but he was having none of that and made the crappy day feel special for her.
x
I don't have much faith left for these two anymore(I sort of oscillate between cautious hope and zero expectation) but I'd be deliriously happy if we got another capital-letter Keenler scene this season too.