If this is your first foray into Windows, stick with 7 Professional if you can get it. Personally, as long as you can remember to avoid the stupid "pulldown splitscreen" action on the desktop, Windows 8.1 is a better choice (Professional, naturally). You really don't want Windows 10 being your first trip into that OS purely because of the always on/forced updates. You will end up in a situation where you get the inevitable "infinite boot loop" where Windows 10 forces a driver update that breaks your system and BSODs you, then Win 10 reverts to the last saved point before the update, attempts to reapply said broken update (because forced updates you cannot disable), and you get that lovely loop of doom.
And no, it isn't a fairytale. I've seen many friends afflicted with that situation, including my dentist who had the misfortune of thinking Win 10 would work for him only to have one of his dental imaging software drivers forcibly updated by Win 10, thereby sending the computer into perpetual boot loop, thus rendering his medical equipment useless until I reverted him down to Win 7 (the pervasive database software he uses is incompatible with 8.1).
Right now, while 10 has lots of under the hood goodies, it's too much of a problematic hassle for end users whose systems inevitably get a broken driver, thus the situation I just described above. I wouldn't recommend Win 10 until MS gets back to reality and lets us control our drivers again (security updates being forced are fine, but not drivers).