I voted 'keep both'. The team will be completely flushed out in 2010, especially if Curry declines his last option year. The remaining team should include those two plus Chandler and Gallinari.
Why would Curry turn down his last big paycheck? I really think they should trade one, and it has to be Nate Robinson over Lee IMO. Lee is a stud and legitimate PF while Nate Robinson will forever be a 5'9" SG.
Nate has been outplaying Lee though. 16/4/4 off the bench puts him in contention for 6th Man of the Year.