Chains and U-Locks take under a minute to cut with an angle grinder, regardless of brand/make/thickness.
Thicker is better against bolt cutters though, which is more common.

Cable locks stop someone from just walking away with your wheel or seat, does nothing for someone out looking to steal a bike.

I talked to a kid in my neighborhood who was known for lifting bikes, he said he walked around with tin snips and would take a bike locked with a cable when-ever he needed a ride or wanted to make a few bucks.

I'd say cable locks are as useful as a piece of rope.