From what I've experienced of linux installs, would have that should be the case - that a fresh install of 14.04 with update check should be no different to a regularly updated 14.04 install. However, there is a possibility that is not the case. A normal sudo apt-get upgrade will "install the newest versions of all packages currently installed on the system". There becomes a problem though, if an upgrade dependencies have changed, as an apt-get update will not remove packages that are currently installed or change the install status of other packages. However, this can be overcome by running sudo apt-get dist-upgrade, as that will will attempt to work around dependency changes, and may remove packages if things have changed. Since a fresh install is starting from a clean state, there is the possibility that the package dependencies are different, so a completely different install base might be applied. However, I would have thought this sort of major change would have only happened across a major/minor release, not within the same version. I would expect there to be differences between a 14.04 distro that was kept upto date (and was now reportedly a 16.04 install), and a clean 16.04 install, for example.
I hope that more or less answer, or doesn't answer your question!
I hope that more or less answer, or doesn't answer your question!