I just went through this exact same process. I drive a 2013 335 and my wife currently drives a 2011 328. I ruled out the RX350 almost immediately after the test drive. The driving experience simply does not compare to the X3. The Lexus interior is very dated, and their control interface is poor. The BMW free maintenance was also a nice benefit over the Lexus.
I considered the X5 as well, but my wife and I ultimately decided that it was too big for our current needs. We are expecting delivery of our 2014 X3 in a few weeks.
14 x3 28i
13 335 xdrive
11 328 xdrive (ret)
07 335xi (sold)