The previous Hydro coolers use 120 mm and 240 mm radiators with matching fans. The new H90 and H110 use 140 mm and 280 mm radiators with matching fans. The increase in surface area means you can match heat dissipation and air movement with lower speed fans, which reduces noise. This would be good enough, but Corsair also took the opportunity to actually increase performance.
In addition to larger fans and a larger radiator, Corsair also added an enhanced copper cold plate to increase heat transfer. If you are going to have a larger radiator you might as well use it. The kit also comes with braces for both Intel and AMD sockets released in the last few years and the foreseeable future. The Hydro H110 and H90 are available now for $129.99 and $99.99 respectively.