Realistically you're just stopping the "grab and ride" joy riders. Any of these are only minor deterents and basically you can purchase the least expensive item that is easy to put on and remove. Alarm is good because at least it draws attention. Not that anyone really looks or cares... With Disk Locks don't even need to pick up the whole bike, I hear they just put a skateboard under the front wheel. Cables and chain are usually nothing that bolt cutters or a cordless grinder with a cutting wheel can't get through in about 5sec.
Just make sure your insurance is paid up...
