I'm surprised that someone in the IT field would recommend 7.
7 was released in 2009. That's seven years ago. It's old. Mainstream support ended in 2015, so you're not going to be receiving updates or hotfixes for it anymore. It's non-UEFI out of the box, so you're going to have to deal with legacy vs. UEFI during your install. Soon you'll have to deal with legacy drivers and non-standard drivers to fit 7 to newer hardware, just like people had to do with XP when Vista and 7 were released. 7 is a dead end. 10 is not.
The lifecycle plan for 10 is to released large updates (think Windows 8.1) on a semi-regular basis. Instead of focusing on releasing new versions of Windows every few years, 10 will be updated with support for new hardware and appropriate security hotfixes. That's why they did the free thing for a year; they wanted everyone on it because it's THE version of Windows from now on. Windows 11, if it will ever happen, is a long ways off. You'd be absolutely stupid to buy 7 at this point in time.
Speaking from a performance standpoint, 10 is also faster. It takes advantage of the new booting tech introduced with Windows 8, so your boot times should be cut by roughly half on disk drives, and by a factor of 3 or so on SSDs. It makes better use of RAM and cache, so applications typically run faster and open faster as a result.
Now from the "it spies on you, does things you don't want, blah blah blah" bullshit standpoint, it's all settings you can turn off. You can even do it on first boot during the install. It's fucking easy. This has always been a moot argument to me. I don't get why people are so butthurt about having to flick a couple switches.
tl;dr you're braindead if you choose 7