Just so you know, I have received the Vive developer kit.
I have taken it out of the box. It's more elaborate than the Rift, as there are two laser emitting base stations that the headset senses, for positional tracking. In contrast, the Rift developer kit uses a single camera to sense the location of the headset. The reason for the Vive's different approach is that it is designed for room scale VR. For our purposes in a seated simulator, I don't think that is relevant.
The Vive comes with two hand held 3D tracking controllers with a couple of buttons and a trigger on each one. I'm sure they are fun for many types of game but I don't see much use for them in a driving simulator.
So it seems to me the Vive has more capabilities in its current form, but is more difficult to set up.
I had to install Steam in order to install the SteamVR software. Unfortunately that is as far as I have got because the headset requires a power supply but the transformer requires a US socket. It can take up to 240 volts though, so I've ordered a US to UK adapter and hopefully can proceed when that arrives in a few days. For now I've put it all back in the box to keep it safe!