I have an old LR3 install on my macbook pro that I have used very little while making do with iPhoto. However I am now considering moving to LR and was wondering if I should delete the oldLR3 install before upgrading or upgrade on top?
It is not necessary to uninstall Lightroom 3 first.
You can upgrade to Lightroom 6 > install it and upgrade your catalog and once you are used to it, you can uninstall Lightroom 3 to free up space on your system.
Retrieving data ...