I don't know exactly how LiveCD works, but I know that everything is happening on the RAM memory, so a great part of the RAM would be used by the OS itself. Can I really experience performance in a LiveCD context?

I'm trying to decide between Xubuntu 14.04 LTS and Elementary OS Freya (both based on Ubuntu), to see which one would be more lightweight for my machine.

My specs are: Intel Core i3, 2GB RAM, 320 HDD

I've already have installed Xubuntu 14.04 LTS but tends to get veery slow sometimes. It could be anything (dropbox, locate database update, several chromium tabs + opening smth else, slow wakeup after suspended, etc)