iPad - smooth running, just gets on with it. Good, easy to use operating system. OS updates direct from Apple so no worries about obtaining them - some android users with phone contracts don't get updates to the OS because the phone company won't supply them.
Huge range of apps, some very good, many absolute rubbish but that't the same for all tablet OSs. One advantage of the Apple Store approach, where you can only install apps from there, is that it makes it much harder for the malicious to distribute malware.
Also integrates very well indeed with Macs (at last). We use Macs as the only computers now (tried Win10 and hated it), if you're going to be using Windows you'll lose some functionality but I don't know if Windows tablets can work with PCs in the same kind of way.
The hardware is very resiliant, I've given an original iPad Air a huge amount of use since I bought it when they first came out and it's still going strong. I recently got a 9,3" Pro and for most people's computer usage I suspect it would suffice on its own. Noticably quicker than the Air mk 1 as well. Retina screens are superb displays as well. The Apple pencil thing is expensive, but if you're into photography or artwork is really usefull. Add a third party app and it turns the iPad into a very serious graphics tablet.
Downsides. iTunes is necessary, but it's nothing like as bad as many say. Behaves itself well on the whole and isn't a bad media player at all. You don't even strictly speaking need it, but it's useful for local backups of the iPad and getting media and data on and off the iPad. Just make sure the first thing you do with iTunes is go into the preferences and ensure it's not busily moving all your media files, including recordings, to its own library. :-/
Once in a while iPads get confused, a hard reboot, or if that doesn't restore sanity returning them to original factory settings and reloading your stuff is simple, so long as you have a backup.
Siri. Probably better than Cortana, but as far as I'm concerned both are best terminated with extreme prejudice. Unlike Cortana, once switched off Siri stays off.
iCloud. We only use it for syncing a limited amount of data between tablet/phone/Mac. Photos, music and everything else we store locally.
And don't forget your itunes account/Apple user id and password. The stories of bricked iOS devices following major OS updates almost all boiled down to "it asked me for my account password before loading all my personal stuff and I can't remember it".