The answer to that question comes down to what you prefer, I like stability in my distro, and the security to be up to date, and I only have 5 Gigs of data to use a month, meaning I need to be careful about downloads and things I do on here, not to mention it is a shared computer. So LTS works out perfect for me, because I do not need to go on the internet, or hook up and do a major download every 9 months. If you can deal maybe with a couple issues of so and so program not working right away, and do not mind the interface changing often and resetting everything up, you might opt to go with the newest versions. Really important features seem to be back ported most of the time though to the LTS.
This guy gave his two cents on it, and I liked it pretty much, He is a user on the forums too. So for my family and I to use it, we need something that just sorta stays working for a long period of time, without having to do any major upgrades. ( I am going to need to for Xubuntu upgrade soon though, its support ends sooner than Ubuntu, The Security for the Kernel should stay supported till the end of the normal LTS though.)
The beauty of Ubuntu, is it tends not to slow down over time, not like Windows for sure. You do not even need to Defragment it. Just get rid of useless programs and update regularly and it should stay pretty fast. So far having used this distro exclusively for about a half an year or more now, I have not had any slow down in the boot up or responsiveness of programs, even with two DEs on here. (which can add a lot of packages and make it bloated.)
Basically, if you want to be more bleeding edge, and have the latest versions of all the software, go with the newer distro changing them. If you want Stability, and not having to change much on the distros, LTS is the way to go.
And no worries, we all have questions about things and ask, best way to learn.