Ubuntu Linux remains one of the most widely used Linux distributions. Various projects have branched off of Ubuntu, including KUbuntu, LUbuntu and XUbuntu, Linux Mint, EduBuntu and Mythbuntu, differing mainly in either the windows manager (GNome for Ubuntu, LDE for LUbuntu, KDE for KUbuntu, and XFce for XUbuntu, Cinnamon or Mate with Mint) or their particular focus (education for Edubuntu, media with Mythubuntu). 
Other differences may exist in the applications installed with the standard installation, such as for example the package manager (application shop) program used. But all use the same or similar repositories and thus offer the full gamut of open source software available for Linux. There are various other, smaller, derivatives of Ubuntu, focused on specific target uses.
The different windows managers impact the level of resources needed for Linux. LDE and XFce are considered to require low resources, whereas KDE has most eye candy and thus will be noticeably slower on lower end hardware. 
But this is relative. If you run e.g. XUbuntu on a 5 year old net-book with a 4-core processor, 4 GBytes of memory and in which the hard disk drive has been replaced by a SSD drive, then it will start up for a cold start very quickly, or from suspend within seconds.
The windows system also is the resource drain for various uses of Linux. Many people don’t realize it, but their mobile phone will be running Linux with an Android user interface if they have an Android phone.
Many microcontroler based systems, such as the controler in your network attached storage device, your home router, your car navigation system, or the Rasberry Pi also run under Linux, but with either no or an even less resource intensive user interface. Usually such applications will be running either a small web server, or have program present several HTML pages as user interface to allow setting various options. Linux is also very good at multiprocessing and multitasking and thus is one of the most widely used operating systems on internet servers and on super computers. This little tidbits supports the statement that Linux is very scalable, covering the whole spectrum from micro-controller to super-computer.
Linux is a Unix based operating system. iOS is also a Unix derivative with a graphical user interface added to a kernel originally evolved by OpenBSD.
Despite the fact the Android and iOS are seen as very user friendly there is still a high level of resistance in companies and with individuals to try Linux. For some strange reason it still has this aura of geekiness and being difficult to use. In fact, if you have a reasonably widely used computer with reasonably standard hardware, it is highly likely that if you download a Linux distribution and install it on a USB stick following the often excellent instructions on the distributor’s websites, that you can have a Linux based or dual-boot (Windows and your chosen Linux) computer up and running in less time than you would need to install a new version of Windows on a clean computer. In addition you will find that thousands of open source applications are available for free from the repositories to download and install. And these repositories have in fact been the ‘app shops’ for Linux for decades, long before such concepts became better known to the general public as the Google or Apple app stores. You can find anything in there from simple games of patience all the way to advanced statistical systems which can compete with SPSS, and SQL based databases (MySQL, MariaDB), different Office packages (OpenOffice, LibreOffice, Calligra), graphical programs (Gimp, Krita), etc. So far I haven’t found any application in Windows for which there is not a competitive Linux application.
The security model of Unix, and by extension of Linux, has always been better than the Windows security model. Unix was a multiuser and multiprocess system, usually with all sorts of external connections, while windows evolved from a single user microcomputer operating system which originally was completely stand alone. Thus Unix always had to consider security, whereas with windows this had to evolve. One of the most notable differences with Linux vs Windows will be getting used to the fact that all files are owned by someone (a program or a person) and that unless you purposefully reassign ownership, you can’t simply changes files. But even much of this can be done from the graphical shell nowadays and does not add much time or complexity to working within either environment.
If you have a limited budget, or if you are simply fed up with commercial software suppliers increasing their prices for each new version of their offerings without really showing revolutionary changes but forcing you to buy new versions by dropping support for old, proprietary, file formats, then there really is no argument no not trying one of the Ubuntu derivatives. This all the more as you can install Linux next to Windows and can thus simply restart into the other operating system if needed.
If you don’t know whether you want a Linux with lower resource needs or one with maximum eye candy, just install either XUbuntu or LUbuntu as lower resource installations, or KUBuntu as maximum eye candy installation to start with, and start learning your way around a little bit. You can then also install one or more of the other graphical shells from the repositories at and switch between them by logging out and choosing a different graphical shell when logging in again.
Although I started with SuSE Linux and a KDE based long ago, my personal favourate for many years now has been XUbuntu due to its low resource needs. The eye candy is more than sufficient, does not distract from simply getting things done. But this is purely personal. You can find more information and download distributions from the following sites:
Ubuntu: https://www.ubuntu.com/
KUbuntu: http://www.kubuntu.org/
LUbuntu: http://lubuntu.net/
Xubuntu: https://xubuntu.org/
Linux Mint: https://linuxmint.com/
Edubuntu: https://www.edubuntu.org/
Mythbuntu: http://www.mythbuntu.org/