If using multiple monitors with the Surface Pro 3 is all you care about, then I would suggest getting one of those "expensive" Display Port MST hubs (they are really not that expensive). You can use it with other devices.
The docking station for Surface Pro 3 however is more versatile. So if you want extra USB ports, a nice stand, and so on, then the docking station is probably your best choice. But it is limited to that particular device. You may or may not... be able to use it with Surface Pro 4 once it's released. Most likely... if they follow the footsteps of Apple... you will have to invest in a new docking station.
With the docking station, you connect one monitor to the Surface Pro 3, and the second monitor to the docking station. With a Display Port hub, you connect the hub to the Surface Pro 3, one monitor to the hub, and the second monitor to the hub.
Solution 1
Surface Pro 3:miniDP
|-------miniDP-to-HDMI------VN289H:HDMI
Docking Station:miniDP
|-------miniDP-to-HDMI------VN289H:HDMI
Solution 2
Surface Pro 3:miniDP
|-------Hub:miniDP---miniDP-to-HDMI----VN289H:HDMI
|
|-------Hub:miniDP---miniDP-to-HDMI----VN289H:HDMI
Even though you have double HDMI ports on each monitor, I don't think you can daisy-chain them. The second port is usually for one additional signal source, not for repeating the first signal received on the first port. I think only some Display Port equipped monitors are capable of daisy-chaining. (I might be wrong about that. Some HDMI monitors may be able to do that as well.)
I would not recommend using one of those USB based extenders for external monitors. It piggybacks your CPU, and these extenders tend to have technical limitations like low color depth.