Well of course after playing with Xubuntu at home it didn’t take much to have it installed on my work computer, a very old Wolfdale with a Celeron CPU and 4 GB of RAM. A very slow computer for its age, and also relatively old. Not sure exactly but I would guess around 6 years. This has been running Lubuntu up to now. The result of this test showed there is not really a great deal of difference performance wise, at least for the apps I use, between these two variants of Ubuntu. I understand that the memory footprint of Lubuntu itself may be slightly less.
Nevertheless, the window manager in Xubuntu, which is not OpenBox, gives a much cleaner appearance to the operating system, a highly desirable characteristic for someone like me, who finds the interface improvements make for a very clean and polished appearance. The further advantage is that it is not difficult to install sophisticated apps like Google Earth. Therefore it is more of an all round system than either Mint, which is too resource hungry for old computers, or Lubuntu, which has too many components missing to make it easy to install power applications.