Ubuntu have later versions of packages shipped out of the box whereas RedHat backport security patches and bug fixes to older versions.
So for example on RHEL 6 you will find PHP 5.3 which is EOLed by PHP a while ago but still supported by Red Hat. You will still get updates and patches from RedHat but your apps might not work/install and complain about old version of PHP for example. Latest Ubuntu Long Term Support (LTS) release (16.04) ships with PHP 7 out of the box whereas latest RedHat/Centos 7 comes with PHP 5.6.
Nothing is stopping you from installing the versions you want from some other package/software repositires on any distro you like but its best to stick with official ones as you will get security patches and bug fixes as soon as Canonical or RedHat release them. And you want these to come from the vendor and fast, not some third party.
So check what your apps need/support.
Apparently PHP7 is super fast.
You can get enterprise level support for both but RedHat have been doing it for a bit longer so thats probably why they come across a bit more "robust". I doubt you will need it to run a LAMP app though.
Oh and then there are differences between package managers ( apt vs yum), default firewall managers are different and some other things but if you haven't used any of them then it makes no difference and probably best to stick with what you have running already. People get too religious about these things.