Just for reference I am currently using Xubuntu 14.04 and experiencing no freezing in regards to starting applications that were pre packaged with Xubuntu. I have 4GB of RAM and about 650MB are what I regularly use with Firefox open.
What you really need to understand about Xubuntu is that not only is the Desktop Environment which is XFCE light but the applications that come with XUbuntu are exclusively selected based on how much resources they consume (abiword, firefox, parole video player). Using these apps will guarantee you a freeze-free experience, outside of that I don't know how fast or fluid your experience will be with your specs.
Regarding measuring performance in a LiveCD context, you are better off checking benchmarks of the Linux distros online as running on LiveCD will not grant you an accurate measure.
To conclude I would honestly recommend Lubuntu or Xubuntu as both are more lightweight than elementary OS.
Elementary OS recommended requirements (1GB of system memory):
Xubuntu recommended requirements (512MB of system memory):
Lubuntu recommended requirements (128MB of system memory):
Of course when resource consumption goes down so does functionality and with that in mind I have to say that your best option is Xubuntu still but with applications that are less resource intensive.