As Cleggy said, it's your choice, you've got to do what you feel comfortable with. We all have our own in-built scale of acceptable risk vs reward.
Just do it in awareness of both sides of the coin.
There are a number of misconceptions surrounding cages and safety equipment. It's important to understand this when making an informed choice.
A cage is a very hard structure requiring a lot of force to deform. This is both it advantage and it's problem. Unlike trees, lamposts, Armco, etc the cage will be with you in each and every accident at what ever speed. You must therefore dress and adjust the car appropriately, even for the half mile run to the corner shop.
That means a helmet on your head and full harnesses done up properly tight. (Harnesses and seat belts stretch in a crash to help absorb and dissipate the energy and to release the g load on your body. This means you will move around more than you think at serious speed. Move around, and you will be (risking) hitting your own cage.
This leads to the other popular misconception, roll cage padding. I think someone touched on this earlier in the thread. Almost all the proper, (as opposed to pipe lagging from the plumbers) padding falls into two types. A very basic type more beneficial in protecting you if you bump into the bars while climbing in or moving around in the cockpit, of comparatively little use to unprotected body parts in a crash. The more specialist padding designed for use in crashes. This is where the big misunderstanding lies, almost all of this type of padding is designed for use with a helmet. It is not to save your bear skull.
There was one company, in the US, that a member was looking into a while ago that was marketing a padding for helmet less protection, but haven't heard anymore about this since.
For the track, where you are helmeted and well strapped in anyway, a full cage makes a vast amount of sense, in fact, these days, for a mainly track use car, it's the only way I'd go. For the road, it's a big, big compromise, if you're someone that can live with that, excellent! Go for it, (plenty do). Don't, forget, it's passengers as well that will also need helmets and properly done up harnesses.
But do think it through fully first, the classifieds both on here and at the other prime Westfield selling venues are full of those that caged up cars without considering if they could live with them, and simply slowly stopped using them on the road.
The Westfield MSA half cage is probably the best compromise for the road, if you want the enhanced roll over protection it's height and superior strength give.