Security

For what use?

In your garage? Under a cover on your front? At work? 

At home you can't beat a feck off good chain attached to a feck off good ground anchor sunk into 4 inches of concrete in a brick built garage with an electric steel roller shutter door with autolock and a bloody noisy dog.Difficult to take that lot to the shops with you though.

Alarms aren't worth a shit other than as a sop to the insurance companies. Thieves lift bikes into refrigerated vans with the alarms going off and no-one takes a blind bit of notice. They, and immobilisers, stop the opportunist though.

Good chain and lock are good when on your travels so long as you chain it to something immobile. Disc locks will, again, stop the opportunist.

A decent cover that you can thread a lock through - Oxford do one - and then attach it to the aforementioned immovable thing is always better than leaving the key in the ignition too. It makes it harder for the thief to see what the bike is and therefore makes it more likely he'll go somewhere else. Unlucky for the someone else of course.

Just my opinion of course. 

98% of the time I'm right. Why worry about the other 3%.

Falco's right - where for?

I had one of those disc locks with an alarm built in on my old Chundercat, that was great as a casual deterrent, but big chain to something immovable best.  Or chain it to your mates' bikes at an event.  I'd love to see someone trying to lift 4 big old tourers at once!!