It's not a binary thing. The US will put a certain value on getting Assange and that will determine the extent to which they'd be willing to expend resources (including diplomatic capital) on doing so.
I think the value of catching Assange probably dropped a lot post-Snowden though. He's probably more famous, and more importantly he proves that Assange isn't a one-off.
Don't be fooled. Both Assange and Snowden would endure the worst treatment a human being can endure if the US had their way. Just because they don't appear to be willing to do everything to get at them does not mean that if these people fell in their lap that they wouldn't commit unspeakable atrocities.
Having Assange holed up in the Ecuadorian embassy and letting the Swedish thing stew and continue to tarnish his reputation is probably just as good for them.
I think the value of catching Assange probably dropped a lot post-Snowden though. He's probably more famous, and more importantly he proves that Assange isn't a one-off.