Anti virus can be very helpful in corporate environments if set up right and managed by knowledgeable people. Those people are expensive, but they're life savers when John from marketing clicks the "enable editing" button in a spreadsheet he just received from a spoofed email address.

The problem with corporate security is that security vendors often try to shovel as much crap onto your network as possible, rather than set you up with the security system you need. It's not hard to set up a company wide system that shows all green checkmarks and has tons of tray icons running to assure upper management that everyone's computer is now secure, especially with duplicate features and multiple daemons that a talkative sales rep might try to slip in for that sweet commission money. You also need someone competent to look through logs, keep checks on what's going on, and not get fired or demoted if they don't report anything new (because if you're lucky, there's nothing new to report).

For smaller businesses, the best you can do is hope for the best, really. Keep your consumer AV running and try to stick to common security advice, because there's no way you'll be able to get much use out of common business AV products if you don't have someone in your company who knows how to use those tools.

For consumers, Windows defender is often a decent balance. It's pretty good at detecting viruses, doesn't get in your face all the time, and although there's definitely a performance impact, it's low enough that office work shouldn't be affected by it too much. As a dev, I hate how much it gets in the way of many applications (especially those accessing many small files, like compilers), but I realise that this isn't exactly the most common workload for AV.