Oh, this is where I disagree. A wire can be quietly and discreetly cut with wire cutters in seconds. This is no protection at all. It's just inconvenience for you.

What I've been using for years is a heavy chain with a lock (disc-detainer style). The chain weighs around 3.5kg. You can of course cut it with an angle grinder, but have you ever tried cutting a chain with an angle grinder without a vise? The chain slips away and it's really difficult to hold it in place for the cutting, which would take more than a minute.

All those Kryptonite-style U-locks have the disadvantage of being easily fixed in place for the cutting. They are also useless for attaching your bike to large trees, street lights, etc.

Remember that if a bear is chasing you, you don't have to outrun the bear, you only have to outrun your friends. If there are 4 bikes and my bike is the most difficult to steal, I'm fine.