There are two main headsets at the moment. HTC Vive and Oculus Rift.
Oculus Rift 3 sensor is £145 cheaper.
Both have the same resolution. Vive has slightly larger fov, whilst the Rift has slightly sharper visuals. (noticeable in cockpit games where the dials are easier to read on the Rift). Vive has more screen door effect, whilst Rift has more god rays. Again another compromise by both. I personally chose the Rift as i preferred the pros of its visuals, but neither is clearly ahead. My bias is towards the Rift
Vive and Rift have comparable tracking in spaces 3x3m and smaller. Vive supports 5x5m. The Vive has the superior tracking solution here. Rift needs 4 usb ports free, 1 headset and 3 sensors. The Vives only needs 2 sensors for tracking. It frees up usb slots, but will take up plug sockets. As my play space is 3x3m, my tracking is perfect with the Rift.
Rift headset is lighter and more comfortable, however can be a problem for people who wear glasses. Need smaller rimmed ones to fit. Also the Rift comes with headphones built in. I intended to use my own, but quickly appreciated the built in ones as it was just way easier and the sound quality isn't half bad. You can buy another strap for the Vive to add headphones now, that is just raising the cost of the Vive more.
The Rift controllers for your hand tracking are superior to the Vives wands. Some people prefer the Vive wands, but i feel the majority agree the rift ones are better. They are small and fit around your knuckles into your palm. Feels more real to your real hands, whereas i feel the Vive wands make me feel like my hands are holding spoons at times.
Software wise, the Oculus SDK is better than SteamVR. Oculus have been using ASW and Cylindrical TimeWarp Layers to make the VR experience better. ASW basically dropped the minimum spec for vr by a couple of tiers. Cylindrical TimeWarp Layers making text surpisingly even clearer. Vive can use software to be able to use the Oculus store and play any of the games. Just not with the use of the asw etc. Rift can also use Steam. However there is concern about Oculus store. Will your next headset work with it? If not then you wont be playing your old rift games on it. It is still early to know. There is an openvr in development that may change things up. Or other headset developers may allow Oculus low level access to implement their own SDK. I believe HTC won't allow this.
Gamewise i think Rift has the best VR games. Oculus have really put some money into the game development. However, recently Fallout 4 VR released. It is definitely appreciated even though it is a port and lacks a lot of VR refinement. But it is hands down the biggest VR game in size there is. VR still doesn't have its GTA's Witcher sized games yet. Fallout is the first, although not perfect. It is only support officially on the Vive. It will run on the Rift but the controls are not correct and borderline broken. There are tweaks and fixes that can make it a lot more bearable, but very far from ideal situation.
Anyways, my personal opinion is Vive is no better than the Rift (actually think Rift is better package) however the Rift comes with free games and is £145 cheaper.