A crippled Thunderbolt dock I might say. 3 x USB 2.0 only; FW and LAN. It doesn't even work easily with any PC.
And IMO, USB 3 hub, multiple inputs, and flexibility on the Dell makes up for $300 Thunderbolt dock.
Ethernet might matter. You're also forgetting that the TB display has a camera and speakers built-in. It's perfect as a docking station for a portable Mac if you just want to be able to plug in TB and power and have everything else come with it. With the Dell display, you'd have to plug in a USB cable, speakers, a camera, power, and possibly ethernet and FW/TB (in some cases) to the laptop.
But if you have a desktop computer... yeah the Apple monitor sucks for you. Especially if you don't have Thunderbolt. Make a wise decision.