At the core of every Philips Hue setup is the Philips Hue Bridge, which gets a second-gen makeover in the new starter kits. The new bridge is what gets the HomeKit upgrade -- you'll need to upgrade if you want to start controlling your lights using Siri.
They won't shine any brighter at the default, soft white setting, though. Here's the old Hue bulb on the left and the new Hue bulb on the right -- both sit at about 550 lumens at the default setting. You'll need to dial up to a hotter, whiter daylight tone before you'll start seeing any extra brightness.
Of course, the real draw is with HomeKit, and with those Siri controls. Upgrade to the new bridge, and you'll be able to turn lights on or off, dim them up and down, or change their color by asking her to handle it.
The new Philips Hue Starter Kits sell for $200 (while they aren't available outside of the US just yet, the existing versions sell for £150/AU$290). It's a steep price for Siri-powered, color-changing bulbs -- read our full review to see if it's worth it.