I wouldn't advice to upgrade to High Sierra at this moment. Too many bugs. The advantages of Sierra and El Capitan vs Yosemite is that they get security updates. However there can be compatibility problems with older software. My printer Canon 540 Pixma doesn't work anymore, I can't save as reduced size in Acrobat Pro (unless i save the file on an usb stick) and under Sierra I can't open using Office 2011 some old complex Word documents with many graphics and equations and FileMaker Pro 10 quits unexpectedly. Parallels 11 luckily runs on 10.11 and 10.12. I don't want to upgrade because for 6 cores it's too expensive.
I run High Sierra and I suggest an upgrade. High Sierra runs faster and launches apps quicker than the previous Mac OS, especially with those running conventional hard drives.