Peterborough,
According to distrowatch, Linux Mint is the most popular. For reason, I would say. For minimalistic approach, use the Xfce version. I prefer Mate, but each to his own.
http://linuxmint.com/
Based on my experience with Windows, OS X and variety of Linux distros, I can say that neither of them is perfect and each of them has advantages and disadvantages over others, so general comparison just makes no sense. Here is my take on all of them.
For day to day stuff, I use OS X and Mint. Both very stable, no malware headaches, can't remember when I had a problem with either of them. I used Ubuntu, but abandoned it when they introduced that Unity desktop. Hated it. I run Debian on my server, by far the most stable OS I ever worked with. It's not for beginners though and it's definitely not the most suitable distro for your stuff. Fedora is good if you're into the latest developments in Linux world. Again, not the most convenient for your stuff. I also use exotic, Debian-based, highly customized distro for some specialized applications that neither OS X nor Windows can address due to lack of flexibility and inability to use some standard (and insanely expensive) commercial programs the way I need. The biggest advantage of Linux is its flexibility. It's its biggest disadvantage too - which one of hundreds of distros out there is best for you? Good luck trying to figure that one out. I tried maybe 20-25 of them and just scratched the surface. Each of them had something I liked and something I hated.
You can run Firefox and Thunderbird on all major Linux distros. Make sure you isntall Ghostery add-in in Firefox, so you can gain a bit more control when doing your thing
Mac's OS X is the most rigid OS of all. It's beautiful if you don't want anything beyond what Apple gives you. As for hardware, Apple machines are very well balanced and work better out of the box than any PC I ever had. After years of hassle with various laptops, I bought a MacBook Pro and never looked back. Perfect for Mint and my custom Linux, installed side by side with OS X. I just can't believe how well Linux runs on a Mac computer. If you want to go that route, I wouldn't install Linux on the latest Apple models.
I extensively use Windows 7 at work and for professional stuff, it's the king! I find Windows 8 okay if you are just into youtube, FB etc. Don't like those tiles regardless. If you are into professional stuff (e.g. Office), I find it very clumsy. No wonder why it didn't meet expectations.
I hope this will give you some idea how things stand.
