The difference isn’t all that noticeable, to be honest, or at least I’ve never found it so. If you’re using older hardware, you’re going to get an older “experience” anyway. The most user-visible kernel improvements tend to be improvements in hardware support, which is irrelevant if your hardware is already fully supported. However, I don’t do anything fancy with my machines—no full-disc encryption or the like. I usually don’t even need an initram to boot the system. So maybe you would notice something if your machines were more complicated.
(Note that the laptop I mentioned above started out with, um, a 3.x kernel? It gets a new one every year or so. The only kernel changes affecting it that were significant enough to draw my attention since 2008 were a fix in the support for the Broadcom wireless card it carries, and some changes to how hibernation works, which didn’t matter in the end because I basically never did try all that hard to get hibernation working on that machine.)