If reading about these thefts of modern cars has made me realise one thing, it's that these people are usually ruthless and will stop at nothing. They also rarely turn up unprepared.
It's human nature to defend your property, and I certainly don't believe in giving it to them on a plate. I prefer a range of visual deterrents, burglar alarm (real one not dummy box), security lights, crook lock or disk lock. However, if they ignore all this and decide to help themselves anyway, then they really mean business and probably won't think twice about clobbering you if you get in their way.
I've also read if they suspect the vehicle has a tracker they aren't averse to tearing it apart to find the receiver. If they did that, would you want the car back? I'm not sure I would.