Protection vs. Mobility
I'm a believer in the more ballistic protection, the better—without compromising mobility. For patrol, this means concealable body armor. For SWAT, this means full coverage tactical vests with plate(s), groin and arm protection, helmets, shields, and Armored Rescue Vehicles, along with "ballistic" eye protection, gloves, knee/elbow protection, and boots.
When it comes to individual armor—for both SWAT and patrol—I'm a believer in mandatory wear policies, rigorously enforced. For shields and ARVs, each team should decide its own deployment policy. Most SWAT teams follow these guidelines already.
I've talked with a few teams and trainers who believe in mobility over protection, so they advocate SWAT team members wear only the minimum protection (i.e., personal body armor). Their rationale is SWAT should always be able to overwhelm any opponent through speed and surprise.
But I question whether these advocates have ever been in real-world shootings. To think speed and surprise can work 100 percent of the time is unrealistic at best and downright dangerous at worst. And such thinking will very likely end up getting someone hurt or worse.